How cross-section area of single E-M wave looks like?

In summary: It will be our minimal distance from which we can still say that there is a single E-M wave present. If we moved electron even closer to source, we would not be able to see single photon anymore as it would merge with other waves. That's why amplitude of E-M wave decreases as we move away from source. In summary, in order to convert energy flux [W/m^2] to energy [J], we need to multiply it by time (T) and by area. The area we are interested in, the area our illuminated object has, the area of the slit through our plane wave has passed.
  • #1
gfgts250
14
0
This question has been asked probably many times, and is inspired by area that appears in denominator of energy flux unit [W/m^2]. From what i have read so far, i come to conclusion, that this post should, first of all, try to explain that this question makes some sense.

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First thing that should be explained is FIELD AREA (e.g. electric field area). We can substitute into mathematical expression of Coulomb's law (F = k * q1q2/r^2) any distance (r), and we always get specific force value. That's the reason for which is often assumed that the field is INFINITE. But it doesn't mean that we can not talk about it's shape and size. By assuming some numerical value (E) of electric field, we can draw an outline/contour (bounding surface) by connecting all the points in space around charge having this value [Pic. 1]. So, we've already got shape of the field (spherical, oval, etc.) and it's location relative to electric charge. Additionally, if we repeat this procedure for stronger charge, we can start talking about size, at least in comparative context (in this case: cross-section area of 2 times stronger charge will be 2 times bigger). We can also verify that all of this applies to any boundary value (E). So even if we substitute infinity for distance (r) or 0 for force (F), these rules will be fulfilled - it just mathematiacal apparatus we use, can not cope with such types of values. In other words: infinity of interaction doesn't mean that we can not talk about size of electric/magnetic field.

Let's imagine that we've a simple antenna [Pic. 2a] - piece of straight wire in vertical position. In this antena there is an electron (for this moment just one) which can move up and down. Doing so, it generates an electromagnetic (E-M) wave radiating in all directions (for simplicity let's constraint this model to 2 dimentions, like top-view picture [Pic. 2b]). I'm using this model intentionally because it's the best one I've found so far (unfortunately i don't remember address of that thread), in an attempt to explain absurdity of question about E-M wave's surface. The best doesn't mean correct (more precisely: not complete). Anyway, i use it because it provides a good base for further analysis.

This model shows that in practice we never generate a single E-M wave, but rather we are dealing with radiation which, at greater distances from the source, turns into almost PLANE WAVE (curvature of wave front decreases, area covered by radiation increases). That's why answer to the question "How to convert energy flux [W/m^2] to energy [J]?" often is: Multiply flux by time (this is understandable) and by area. What area? The area we are interested in, the area our illuminated object has, the area of the slit through our plane wave has passed - in other words: ANY area we want. It's easy to understand in context presented before, but usually it's not the intention of those who are asking. The question concerns the spatial size(extension) of field (e.g. electric) of SINGLE E-M WAVE with some given amplitude.

A single E-M wave? What does it mean? Does something like that even exist? Look at the picture, there are two patches/areas [Pic. 2] A1,A2 (at different distances from source) by which a couple of rays (let's consider that they are our single E-M waves) coming through. According to energy conservation law, the same amount of energy has to pass through both of them. So, the only possibility is to lower E-M wave amplitude, and this, in turn, is only possible by moving apart our rays, relative to each other. This process can be seen as opposite to interference. In the latter, when two separate waves approach each other, they E-M fields become indistinguishable and result is treated as a single wave (with doubled amplitude, of course). When moving apart, there should be some minimal distance from which we would be able to see two separate waves again.

But we also know, that all E-M radiation is quantized, it can not divide indefinitely - it can do this just up to the photon level. We should perform a simple experiment: Let's move our electron a little bit (for example: one time up and down - or something like that), just to generate a smallest unit of E-M radiation we can (the shorter the better, in ideal case it will be the shortest unit of E-M wave which can travel freely in space, but it's not a must). We know how much work we have done and how much energy E-M radiation has. We have to divide this by energy of single photon and we've got number of photons in the system. Let's define some minimal distance on projection screen (our measurement equipment) we can distinguish one photon from another and multiply it by photon count. We get some length, this is circumference of a circle. We just have to calculate the radius - distance from radiation source where we should perform our measurements (place projection screen there).

Now, everything depends on what pattern we will see: (1) single photons distributed evenly along screen [Pic. 3a] - it means that photons are generated with uniform spatial distribution of direction - direction of momentum, or if you like: direction of wave vector. It may be partially the result of some hyphotetical process like, let's call it for example: quantum dispersion (photons can diverge sponaneously, with some probability), but in practice it should have different characteristic [Pic. 4a] (be recognizable) then geometrical (dominant) one [Pic. 4b]. Conclusion: indeed, there is no such a thing like single E-M wave/ray in this dimension. In case (2) photons concentrated around some specific points [Pic. 3b] - it means that there are some predefined radiation directions (for example, due to the fact that angles are quantized in some way).

In case #(2) we've got already our single E-M wave! In case #(1) we have to continue searching in other dimensions. Let's generate again some smallest unit of E-M radiation, if photons hit exactly the same places as before [Pic. 3c], then we have found even something better: a single E-M wave with the smallest possible amplitude (stream of photons following each other with properties of continuous E-M wave). This can be called not only single but rather elementary E-M wave. If this also fails, it's time for last resort: so far our example has operated in 2-D (two dimensions) - it was like one slice. We have to take into account third dimension. There are other electrons in vertical wire (below, above), and they move synchronously with the first one. In this dimension, for this type of antenna photons/rays shouldn't diverge from each other (at least they should do it with different charachteristic - slower then in horizontal plane). If such photons are horizontally aligned (with those generated at other altitudes), we should be able to see vertical stripes on the projection screen [Pic. 3d]. Even if we can't get continuous wave this way, we still get a piece of such single wave. This is something more then a photon. A single photon is to small to perform measurement on it, but this piece of wave can have measurable amplitude (this is still a bunch of photons but with limited horizontal distribution - a "thin" wave) and it's E-M field strength is enough to extend to measurable sizes (E-M field is continuous, it can not just drop instantenously in one place. The stronger the source is, the larger is the area that can be detected using standard methods).

How to test all of this in practice? Maybe we don't have to perform all those measurement hundreds,thousand or millions miles away from the source of radiation (Note: Please, treat the following examples only as a theoretical, they are just to show very general idea, not real techniques). First, we can filter tight slice from radiation emitted in all directions (we can use narrow slit) - this will be our initial ray. Then, we can use for example two opposite mirrors to filter it further [Pic. 5a] (simulate longer distance). In theory, light can travel between them almost indefinitely (attenuation if present should be uniform, and maybe even can be helpful in faster reaching the final conditions). Perfecty flat surface of mirror doesn't change angle of incoming ray, just direction (the angle of incidence equals to the angle of reflection), so all we have to do is to wait for a while. If we worry about the interference of rays (incidented and reflected), we can use different mirror's configuration [Pic. 5b] . We can take advantage of the fact that we are only testing small fragment of wave not continuous one, and this fragment has to be shorter then 4L (ray can travel inside box xN times, and later be released on demand). You should also notice that all those mirrors are small, it allows rays diffracted too much to escape from box and without producing too much mess (E-M noise) inside. As i said, it was just theoretical example. Maybe there are better ideas? Anyone knowns about any similar experiments or can recall any knowledge/facts I've missed?
 

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  • #2
Wow - you seem to be very confused - was there a question in all that?
I'll have a go with what you talk about, see if I cannot give you the right words at least, and show you where you seem to be tripping up.
But I cannot tell what you are asking here.

gfgts250 said:
This question has been asked probably many times, and is inspired by area that appears in denominator of energy flux unit [W/m^2].
That would be the units of flux density ... flux per unit area.

First thing that should be explained is FIELD AREA (e.g. electric field area).
Why-ever would you want to do that? What use does the concept have?
The area in the flux-density units is not the area of the wave/field itself.

But it doesn't mean that we can not talk about [an EM field's] shape and size. By assuming some numerical value (E) of electric field, we can draw an outline/contour (bounding surface) by connecting all the points in space around charge having this value [Pic. 1].
This is correct, you can use surfaces of constant E to describe EM fields.

Since electric field is a vector that is not terribly useful in general; better to use equi-potential lines.

So, we've already got shape of the field (spherical, oval, etc.) and it's location relative to electric charge.
We would call that sort of concept the "geometry" of the field - the specific geometric properties you have described (spherical, oval etc) may be called it's "symmetry", though there are more precise terms.

Additionally, if we repeat this procedure for stronger charge, we can start talking about size, at least in comparative context (in this case: cross-section area of 2 times stronger charge will be 2 times bigger).
Nope - that concept does not translate.
For a point charge, the "line of equal E" would actually be a surface - a sphere to be exact.
The sphere for the same magnitude of E, for a charge 2x, would have twice the radius and thus 4x the surface area. Similarly the crossection of the constant-E surface would be 4x.

Let's imagine that we've a simple antenna [Pic. 2a]... This model shows that in practice we never generate a single E-M wave, but rather we are dealing with radiation which, at greater distances from the source, turns into almost PLANE WAVE (curvature of wave front decreases, area covered by radiation increases).
A plane wave is a single wave.
A wave that turns into a plane wave at long distances is still a single wave.

We are able to represent a wave as a superpositon of other waves.
The usual way to do this is by a Fourier Transform.

That's why answer to the question "How to convert energy flux [W/m^2] to energy [J]?" often is: Multiply flux by time (this is understandable) and by area. What area? The area we are interested in, the area our illuminated object has, the area of the slit through our plane wave has passed - in other words: ANY area we want. It's easy to understand in context presented before, but usually it's not the intention of those who are asking. The question concerns the spatial size(extension) of field (e.g. electric) of SINGLE E-M WAVE with some given amplitude.
That is correct - converting the flux density into energy received will not answer questions about the geometry of the wave. But it is not supposed to.

The person asking is using the wrong words to ask the question.
If they mean to ask about spatial extent of a single EM wave, then they should not ask, as in your example, "How to convert energy flux..." That's just nonsense.

A single E-M wave? What does it mean? Does something like that even exist?
The existence of EM waves is well established empirically so "yes" EM waves exist.
"a single e-m wave" refers to a particular solution to the EM wave equations.

Look at the picture, there are two patches/areas [Pic. 2] A1,A2 (at different distances from source) by which a couple of rays (let's consider that they are our single E-M waves) coming through.
You could but this would be an erroneous interpretation of the picture.
The lines in the picture represent rays, not waves.

But we also know, that all E-M radiation is quantized, it can not divide indefinitely - it can do this just up to the photon level.
Careful not to mix up models here.
Photons belong to the particle model of light, while EM waves belong to the, well, wave model.
Also - individual photons may have any frequency, and, thus, and energy.

You are just confusing yourself more and more after this.
I think you need to ask your question.
 
  • #3
I have two simple requests: please, read entire post first, then answer. And don't say that somone is confused just because you don't understand what he is talking about. Who knows maybe i was wrong at some point, but rather not confused.

Let's start with most basic thing.

Simon Bridge said:
I think you need to ask your question.

My question is very simple: For E-M wave with given frequency (v) and given amplitude (A), please draw me an outline (it would be surface in 3D, but we are talking about cross-section, so let's constraint it to 2D) of electric field surrounding E-M wave for some given value (E).

If i ask this question for electric charge, it would be perfectly understandable. The answer is exactly on the [Pic. 1]. We've got an electric charge center, concentric circle around it where electric field = (E) and even specific vaue of radius (r) calculated from Coulomb's law. Now, I'm asking for the same for E-M wave. Of course, the concept of single E-M wave is needed for this question to be valid. And this is what I've tried to prove (define), for the larger part of my original post, that something like single E-M wave could really exist.

Now let's proceed to main explanation. This is the most important part, we have to agree on that somehow before further discussion.

A plane wave is a single wave. A wave that turns into a plane wave at long distances is still a single wave. We are able to represent a wave as a superpositon of other waves. The usual way to do this is by a Fourier Transform.

The last two sentences are correct. The first two not so much (everything depends of knowledge one has).

Let's imagine that in dark room there are two identical lasers. Beams generated by them are parallel. At the beginning lasers are standing at some distance (for example: 1m) from each other. You should be able to define the boundary of each beam - it will be an area of lowest intensity of light your eyes can detect (of course, it will be imaginary boundary depending on precision of measurement instrument, but for for what i want to show, that's ok). If you can define boundary it's obvious you can clearly see two separate rays. Now, let's bring our lasers close together. When they become collinear (i mean they rays become collinear) you will be able to see only one beam but 2 times brighter (higher amplitude). And this is exactly how interference works (or superposition of waves if you like). You can also reverse entire procedure (split rays) and again you will see 2 separated rays (you can say: 2 times dimmer then the original one).

These were two opposite cases. But there is yet another one - quite interesting for us. Move beams very close to each other but NOT too close, there should be some distance between them (let's assume half of visible beam width should be ok). Your eyes should see a WIDER ray (not bigger but wider in some specific direction). Look at the [Pic. 1], when you bring closer those charges their electric fields (where E is considered boundary value) overlap. An outline (line where electric field = E) will surround two charges and will become oval like.

If you repeat this procedure: add more rays in horizontal and vertical directions you should get larger area of nearly (true plane wave has infinite dimensions) uniform intensity. And this is exactly what we are calling PLANE WAVE - previously we've just seen very small part of it! This is even how our base laser's beams are build (you can think that there are many smaller rays inside beam, some perfectly and some nearly collinear). We would be able to split them too, but in our example we don't have technical means to do that.

There are physical processes where such splitting naturally occurs (at least in one dimension). One of them is radiation emitted by antenna [Pic. 2]. One more time, let's position our lasers such their beams become collinear. Now start rotating one of them by some angle relative to the other. You would be able to see, in the same time, the 3 cases described previously. Near the axis of rotation (stage 1) you will see one ray with higher intensity (amplitude), at grater distances (stage 2) this ray becomes wider but dimmer and finally you will see 2 separated rays (stage 3) each one with 2 times lower intensity then ray in stage 1 (by the way, looking at stages 1 and 2 you can see how energy is conserved - how higher amplitude changes to wider area. Energy flux has to be the same, and there are two independent variables in equation: amplitude and area).

And this is the KEY POINT why we can't understand each other! The example using laser rays was a little bit artificial (but useful). In practice (pure wave interpretation) stage 3 should't exist, it would be rather stage 2 with wider area and lower amplitude. In such interpretation initial ray can be seen as consisting of infinite number of smaller rays each one with infinitely small amplitude There is no way to distinguish one from the other, and probably that's why you are calling this: a SINGLE WAVE (which is changing it's geometry with the distance). Well but we are not living 100 years ago, and we do know from "Photoelectric effect" experiment performed circa 1900, that light (E-M radiation) is QUANTIZED. It can not divide indefinitely. So stage 3 has to naturally appear! That's a fact. We know that energy coming through unitary area has to diminish with distance from the source of radiation. We know precisely what energy single photon has (E = h*nu). We know that photon can not be divided. Conclusion is obvious. Wave-particle nature of E-M radiation doesn't mean that you can arbitraly neglect some properties (there are NOT two separate models between which you can freely choose. There is permanent dependence between them).

Let's assume we've got an area with size of 1 m^2, we can calculate distance from radiation source (with known power) where energy coming throuh such erea equals energy of single photon. And from the fact, that photon can not be divided, we know that all energy has to be concentrated at one small point on such area. This is the consequence of the quantization, otherwise the energy should be spreaded evenly. Probability of finding photon could be uniform for such area but photon itself has finite size (like size of electric field used previously). Also electric field around photon is not uniform (decreases with distance) like it's uniform for ideal plane wave.

Honestly, we don't really know how those photons are arranged relative to each other (i've shown a couple of simple patterns [Pic. 3]). Even if they spread perfectly uniformly ([Pic. 1a])), they are doing so only in one plane (for assumed type of antenna). So, it's possible that there are factors causing photons to concentrate around some centers (for example stripes, like on [Pic. 3d]). And concentration area of photons is nothing more then: E-M WAVE (a bunch of photons going in the same direction)! And this is what I mean by saying about SINGLE WAVE. Now, i hope my question becomes clear to you. Why do we need all of this? Because the best (and maybe only) way we can learn something more about nature of E-M radiation is to examine E-M field around it. We still don't known much about it.

At the end, let's deal with the rest:

That would be the units of flux density ... flux per unit area

http://en.wikipedia.org/wiki/Energy_flux
"This is SOMETIMES called energy flux density, to distinguish it from the second definition"
Unit I've given [W/m^2] speaks for itself.

Why-ever would you want to do that? What use does the concept have?
The area in the flux-density units is not the area of the wave/field itself.

It has nothing to do with flux density. I've only said that questions about cross section of E-M are OFTEN INSPIRED by [m^2] that appears in flux density unit (there are a couple of threads at internet forums where others are asking about cross section). Of course, I'm still interested in such areas but not due to flux density interpretation.

My fault, I should rather say: "First thing that should be explained is what FIELD AREA means to me". Why do I want to do that? Because, lack of explicit limit of interaction (like in Coulomb's expression) causes some pople to think that we can not talk about anything, just sit and cry. This is also what I've learned reading other threads.

Since electric field is a vector that is not terribly useful in general; better to use equi-potential lines.

Well, later when we will be taking about fields of E-M wave, those vectors can even be changing with time, so why not to use derivative of vectors, or something like that (sorry I'm not good at math)? Seriously, I'm not doing any calculations with it. In the last sentence of second paragraph there is the main and only reason i was doing so: "...infinity of interaction doesn't mean that we can not talk about size of electric/magnetic field..." All of this was just to show that we can talk about SIZE. How we can define it? At this moment it doesn't matter.

We would call that sort of concept the "geometry" of the field...

Look at previous question and replace word SIZE with SHAPE...

Nope - that concept does not translate.
For a point charge, the "line of equal E" would actually be a surface - a sphere to be exact.
The sphere for the same magnitude of E, for a charge 2x, would have twice the radius and thus 4x the surface area.
Similarly the crossection of the constant-E surface would be 4x.

Look at the expression: F = k * q1q2/r^2

F has to stay constant as well as k and q1 (or q2 - one of them). So if you double q2 in numerator, you have to double denominator, and because r is squared you have to choose such value for r, which squared gives you two times bigger value then previous squared r.

Let's assume that previous value of r was 1, 1^2 = 1, now you need value that squared gives you 2. And this vaule is about: 1.4, (1.4)^2 = 2. So, radius of 2 times stronger charge will be 1.4 times longer.

From my original post: "cross-section area of 2 times stronger charge will be 2 times bigger". Cross section of sphere is circle, and area of circle is: Pi * r^2. Now, substitute values from previous calculations and you will get the answer.

By the way: it's not about cross section, area, radius, volume. It was just an example, just to show that those values stay in SOME relation, that we can compare them for different charges and talk about SIZE of charge.

Careful not to mix up models here. Photons belong to the particle model of light, while EM waves belong to the, well, wave model. Also - individual photons may have any frequency, and, thus, and energy.

No, no ,no. You can't say that. As i mention previously, there is only one physical process responsible for whole E-M phenomenon. Division on particle model of light and wave model of light is artificial. We people are still trying to figure out everything about it. Such separate models temporary exist because we can't combine today's partial knowledge into one coherent whole.

You can't choose between models. You are not choosing anything, rather you are IGNORING some aspects of real E-M radiation!

Well, there are some situations when you can do so. For example when doing engineering calculations (designing antennas, optical apparatus or so). But condition is: Energy of E-M waves has to be much higher then energy of single photons. When energy of E-M wave with given frequency starts to approach energy of single photon of such frequency, something very interesting should happen. And this is exactly what I'm trying to analyse.

Of course photons may have any frequency, but it seems to me that you don't know exactly what you are talking about. Monochromatic E-M wave with given frequency consists ONLY of photons with such frequency! You can easily see this performing famous "Photoelectric effect" experiment (the first one revealing particle nature of light - this is how concept of photon was born). The so called stopping voltage depends on energy of photons colliding with electrons. And you can control energy of photons by choosing frequency of incident light. There is different stoping voltage for red, green and blue light.

In our example with antenna we are generating E-M wave with specific frequency, so we know exactly what energy photons building our E-M wave(s) have and at what distance from the source we should see them.
 
  • #4
gfgts250 said:
I have two simple requests: please, read entire post first, then answer. And don't say that somone is confused just because you don't understand what he is talking about. Who knows maybe i was wrong at some point, but rather not confused.
Please read more carefully - I did not say you were confused anywhere in my response above.
I said you seemed to be confused. Spot the difference.

You were indeed wrong on many points, which may explain why you seemed confused.
You also are having trouble with the terminology - perhaps English is not your first language?
That would also explain why you seem confused.

Let's start with most basic thing.

My question is very simple: For E-M wave with given frequency (v) and given amplitude (A), please draw me an outline (it would be surface in 3D, but we are talking about cross-section, so let's constraint it to 2D) of electric field surrounding E-M wave for some given value (E).
This is not a question, it is an instruction ... and a very unclear one.
What are you trying to acheive?

If i ask this question for electric charge, it would be perfectly understandable.
You have not asked a question yet. What is the question?

The answer is exactly on the [Pic. 1].
The answer to what?
You are not making sense.

We've got an electric charge center, concentric circle around it where electric field = (E) and even specific vaue of radius (r) calculated from Coulomb's law.
You are saying that a line of constant electric field magnitude about a point charge is a circle.

Do you understand that diagrams like pic1 are not normally of constant E, usually such diagrams show lines of constant potential. Switching to electric potentials may help you but I cannot really tell because you have not asked a question yet.

Now, I'm asking for the same for E-M wave.
You want a line of constant E for an E-M wave?
That is drawn the same way - except now the geometry need not be so simple.
i.e. if you have a spherical wave spreading out from a point source, the magnitude may look like this:

##E(r,t) = A\sin k(r-ct)## (in spherical coordinates)

The surfaces of equal E are concentric spheres - the 2D version will have concentric circles.
The circles/spheres travel outward at speed c.

Of course, the concept of single E-M wave is needed for this question to be valid. And this is what I've tried to prove (define),
Proving is different from defining - which do you intend?
This is the sort of statement - where you conflate two different things - that makes you sound confused.

Similarly: in optics, a ray and a beam, are different things.
You appear to be confusing them but it may be you are just trying to use a language you are not familiar with.

Anyway - the topic is too big for these forums. I could go through an point out each place where it looks like there is some sort of mistake, where you may have got it wrong in some way, but that would take too long. It would really really help if you would just ask a question.

Unless you ask a question, I cannot help you.
 
  • #5
I am also confused. You seem to be asking about the size/shape of an EM wave that contains the energy of a single photon. Is that correct?
 
  • #6
gfgts250 said:
My question is very simple: For E-M wave with given frequency (v) and given amplitude (A), please draw me an outline (it would be surface in 3D, but we are talking about cross-section, so let's constraint it to 2D) of electric field surrounding E-M wave for some given value (E).

You have some misconceptions here. First, it is important to note that a single photon does not necessarily have a single frequency. This was the first idea from the 1930s, which considered a Fourier decomposition of the light field. A single photon just means you have a fixed particle number, but that state can be polychromatic.

Having said that: The em wave associated with a single photon can have any shape you like. It depends on the emitter. It can be spherically symmetric or directed. Its temporal duration will be connected to its spectral distribution using a Fourier transform. The power spectral density and first order coherence function form the Fourier transform pair. It is a well known textbook fact that the single photon character does NOT appear at all when looking at the field alone. In fact, there is no way to say whether a field is classical (like a laser) or non-classical (like a single photon) just by looking at the fields alone. You need an intensity-sensitive measurement in order to determine that. Therefore, contrary to your claim the fields themselves are not of particular interest in quantum optics. Their higher-order moments are more interesting.

gfgts250 said:
Anyone knowns about any similar experiments or can recall any knowledge/facts I've missed?

Pretty much every major development in optics starting from the 1960s. It looks like some kind of introductory review might be beneficial. Roy Glauber's Nobel prize talk might be a good starting point: http://journals.aps.org/rmp/abstract/10.1103/RevModPhys.78.1267. It is free to read. However, these forums cannot replace a thorough course in quantum optics - including the math.
 
  • #7
Drakkith said:
I am also confused. You seem to be asking about the size/shape of an EM wave that contains the energy of a single photon. Is that correct?

Not exactly, but close. Your statement could be very good starting point for explanation.

Let's suppose our antenna in [Pic. 2a] has radiated some finite amount of energy (it has broadcasted by short moment). This energy propagates from the source in all directions in some characteristic way (characteristic to spherical wave). The same amount energy has to pass through larger and larger areas with distance from the source (see [Pic. 2b]). It's even more convenient to formulate it this way: Energy passing through some unitary area (for example 1m^2) is smaller and smaller with distance from the source. So, as you can see, at some distance, we naturally come to the point where energy passing through our 1m^2 equal energy of single photon (photon with the same frequency like our E-M wave of course).

And now, we have to decide how to interpret such phenomenon. We already know that light (E-M radiation) is quantized, it can not divide indefinitely, so it's rather not possible to uniformly cover such area with this amount of energy (not possible to divide photon into smaller parts and spread it uniformly) - this is the direct consequence of light's quantization. But on the other hand, it's also not possible photon has such large size (in our example it's 1m but it could be 1km or more, we can assume any size of testing area we just have to choose proper distance from the source) to cover such area (it would not even be able to do this uniformly, since strength of it's E-M field decreases with the distance from it's center). So the obvious conclusion (at least for me) is that with the distance from the source, we should start to see inhomogenities in E-M field passing through our unitary surface, and finally with even greater distance we should be able to detect single photons.

I try to clarify it even more: There are always single photons in E-M radiation, but there plenty of them and such close one together that there is no way we can detect them near the source (photons are bosons - they can exist in the same place in the same time, it's hard to even speak about such a thing like minimal distance between them. We can even say that they are indistingushable from each other). We can only register superposition of their E-M fields and we are used to call it: E-M WAVE. But depending on the characteristic of emitter of E-M radiation, this distance doesn't have to stay fixed. And this is exactly what I'm trying to exploit (the so called half-dipole antenna [Pic. 2] is very useful for that. It generates spherical wave - spherical at least in one direction).

For this type of emitter, from the very beginning, photons are starting to diverge, that's why amplitude becomes smaller and smaller with distance (but of course the total area covered by radiation increases at the same time). But even at the distance 1000 km there is huge concentration of them per unitary area, so we still are seeing uniform radiation (and still can use, for approximated description, the so called: wave model - which could be seen as model describing behaviour of bunch of photons). But with much, much more greater distances (which we can estimate) we are coming to the point, when spaces between photons will be measurable to our equipment, so we just start to see them. It's worth to note, that we are still dealing with the same phenomenon (division on wave model and particle model is artificial, made by people). Accuracy of our measuring equipment (and some laws of physics) has established boundary at which we were able to switch to photon interpretation. Wave didn't change into photons, rather we started to see single photons forming the wave. For spherical wave distance acts like magnifying glass.

Now we've got our photons, but one question remains: how are they arranged relative to each other? Are they spread uniformly, or maybe there are some centers around which they accumulate? It's worth to remember, there was specific reason why photons moved away from each other: Their initial vectors of momentum were different (photon can be treated as a particle, it can have momentum) - their directions were different (this is characteristic feature of spherical wave. For E-M waves generated by laser this phenomenon is not as visible - laser ray can travel longer distances without energy dispersion). So, if during generation, there were photons with exactly the same vector of momentum, they shouldn't diverge from each other. And if they don't diverge, they still should form bunch of photons even at large distances. And a bunch of photons is what we are calling... an E-M WAVE! And this wave is what I've called in my first post: SINGLE WAVE. And I've given a few examples of reasons why something like that could theoretically exist [Pic. 3]. (it's worth some experiment).

Think about photons on [Pic.3] like electric charges. If you superimpose their electric fields , you will get different SHAPE of resultant electric field for each arrangement. Electric field is continuous, we can sample it in different places of space, and this is how we can measure shape. And from shape we can guess arrangement of photons in such wave.
 
  • #8
It appears that you are imagining photons as little particles with vectors that somehow add up to make an EM wave. It is my understanding that the reverse is true. That is, the EM wave is always a wave, and it is just the energy in the wave that is quantized. This is why the emissions from single-photon sources still behave exactly like waves, such as the double-slit experiment. Someone correct me if I'm wrong.
 
  • #9
Drakkith said:
It appears that you are imagining photons as little particles with vectors that somehow add up to make an EM wave. It is my understanding that the reverse is true. That is, the EM wave is always a wave, and it is just the energy in the wave that is quantized. This is why the emissions from single-photon sources still behave exactly like waves, such as the double-slit experiment. Someone correct me if I'm wrong.


That is true. The photon, in QED, is represented as a field that permeates space. Interactions with this field occurs at points and the energy is quantized. Hence, the photon is akin to a classical field that interacts like a classical point particle. The electromagnetic field is an observable. The electromagnetic field of a single photon though is not well defined because the fields are not eigenstates of the photon number state. Only with very large numbers of photons will the electromagnetic field become a consistent observable. So you might as well ask what is the position of an electron in an atom. The answer is that it varies. Each time you check it will be different but after a large number of independent measurements you will arrive at a probability density.
 
  • #10
Cthugha said:
However, these forums cannot replace a thorough course in quantum optics - including the math.

I have started this thread in: Physics Forums > Physics > Classical Physics. I repeat: Classical Physics. And I've done this for reason. For me classical physics includes also : black body radiation, Photoelectric effect, generally everything until the year circa 1920. Quantum nature of light (it consists of some quantas) was then already known, but today's interpretation (generally: Quantum mechanics) was not born yet. It doesn't mean that i believe in "Old quantum theory" or something like that. No. The only information i need is: Light is not just a wave, it's build from some quantas. That's all.

Don't get me wrong, i don't blame you for anything. All of this is 100% ma fault, because I've used one specific word: PHOTON. And this is probably the reason, why you are here.

According to my knowledge, up to circa 1920, chunk of light was called: QUANTA OF LIGHT. Term PHOTON was invented for newer interpretation just to distinguish it from this QUANTA. So i can not blame you that you are taking about quantum physics. But, try to understand me, using term: QUANTA OF LIGHT will create even more mess here. So i will stay with the term: PHOTON. Hoping, that everyone now knows what this term means to me.

Quantum physics in not needed here, i haven't asked for this! Even if I'm wrong it would be easy to explain it without that! There is enough mess here even without quantum mechanics. If you think otherwise, please go away.

You have some misconceptions here. First, it is important to note that a single photon does not necessarily have a single frequency...

I didn't said anything like that. And even don't want to speculate how photon is build. I've only said that photon (quanta if you like) is some chunk of energy. I don't even know if itself has ANY frequency, if we can speak about frequency of photon. All i know is that E-M wave with some specific frequency carries chunks with some specific energies (E = h*nu - i assume nu is the frequency of the wave from which the photon comes from, the only known property of photon to me is it's energy).

We also know from Photoelectric effect that monochromatic E-M wave with some specific frequency carries ONLY photons with ENERGIES specific to that frequency. That's why when we illuminate some material with one light (for example green) current flows in circuit, and when i do the same with other wavelength (for exampe red) it's not. So it is not so monochromatic E-M wave can consists of photons with different energies only arranged in a way that gives us wave with our base frequency. This is exactly what Photoelectric effect tells us.

In some specific conditions photon may change it's energy (turns into different photon) - good example is Compton experiment, but: first we don't know if we can use word: change - it could be different photon generated after absorbing original one (we are talking about Compton experiment). And second and most important to us - it can not change spontaneously. There has to be some interaction - like collision in Compton experiment. If it wasn't true, we could find at least a small amount of photons of some specific energy in any type of E-M radiation (see Photoelectric effect). In my examples, we've already got some set of photons in beginning. There is no interaction with anything and photons are rather transparent for each other. So we should be sure that there will be foton change in our analysed system.

And the second thing i said about photons is that OUTSIDE E-M wave they can be localized. I repeat: OUTSIDE - this is very important (i'm not sure if we even can speak about photon inside wave). So outside wave they have some properties of particles - we can measure its position (with some limited accuracy of course) and even direction of travel.

All those 2 properties, i mentioned, were known before 1920 and also they are not even main topic of my posts. I'm not talking about shape of the photon here. I'm talking about shape of standard E-M wave. Quantum physics in not needed here.
 
  • #11
Drakkith said:
It appears that you are imagining photons as little particles with vectors that somehow add up to make an EM wave. It is my understanding that
the reverse is true...

I didn't said I'm imagining photons as little particles. I see them as the chunks of energies. I've assumed (and that's a fact) - that outside E-M wave they have PROPERTIES of particles (size, position, etc. - we can localize them). But those properties apply also to those little waves (as you said you see photons). Such little wave (wave-packet?) also has to have finite length - so you have got already size. And also it can traval in some direction, as ray of light do - so here is the second property: direction of motion represented by vector. And this is probably the reason you think I'm imagining photons as little particles - I've used word: MOMENTUM which is generally associated with particles. Well, you can replace it with WAVE VECTOR if you like. I just wanted to indicate their direction of travel somehow.

If you really want to give photon some geometrical form then yes: a small-wave is of course preferable one (also for me). It maintains properties of particle and explains some other effects. But it was not my intention to assume some shape of photons.
 
  • #12
Simon Bridge said:
i.e. if you have a spherical wave spreading out from a point source, the magnitude may look like this... The surfaces of equal E are concentric spheres - the 2D version will have concentric circles.

EXACTLY! Yes, this is exactly what I'm asking for! I mean general idea is correct.

Let's continue with your spherical wave spreading out from a point source. Surround this source with spherical, opaque (for this wavelength) shell. There will be no E-M radiation outside it. Now drill a little holl in the shell and some single ray/beam? should appear.

Now, for this ray/beam do exactly the same, what you've done for point source before. If I'm right, the result will be a circle (2D version) on a plane perpendicular to ray/beam direction. Of course, this circle will be periodically changing it's size, but currently it's not such important.

That's not all. Cut narrow slit somewhere else in the shell and second ray/beam? will escape. You know what to do. Result will be similar to the previous one. You should describe me this like, well maybe not exactly squere but something similar to an ellipse (a shape extended in one direction).

But why to do all of that?!

Well, because life is cruel and sometimes you are getting results without causes. Suppose that I'm just giving you these two rays/beams and you have to guess which is which. How will you do this? Hint: E-M wave is nothing more then electric/magnetic field fluctuations which propagate in space. So what you can do? The only thing you can do is to measure such field!

And this my post all about: I suppose that in E-M radiation generated by antenna [Pic.2] could (i don't know for sure) be something what I've called: SINGLE WAVE (if exists, we should be able to see it at larger distances). I've told why i think so. And now I'm asking if anyone heard about something like that. If anyone know about some results of experiments, showing heterogeneity in intesity of radiationat at larger distances. Such heterogeneities should form some shape and this will be the shape of our single wave. What other question then about shape of E-M field can i ask? The shape will tell me what kind (if any) of relation between photons exists in source radiation.

By the way, question about shape is not such abstract like you may think. It's like analysing ray/beam of laser (such things are performed nowdays - of course for different reasons then my). You are placing detector at the front of ray/beam and you are registering intensity (in other words: strength of the field). It could be said: you are taking picture of ray/beam. And then, you are connecting points with the same intensity on the picture. And the result will be some SHAPE. Field is continuous, so no matter what reference intensity (E) you choose, the shape generally will be the same (it could be just smaller or bigger).

Can we agree, at least on what I've said?

perhaps English is not your first language?

Please read more carefully - I did not say you were confused anywhere in my response above. I said you seemed to be confused. Spot the difference

Of course english is not my native language (it's not hard to guess that) - but I'm afraid it has nothing to do with confusion.

I try to carefully analyse your statement You've said: "seemed to be confused" not "be confused". But why? If "confuse" is such neutral word, why to use "seem to"? I see that there is some difference. The question is, do you know what this difference means? This is the language politicians and lawyers are using. But they are not doing so to respect someone's dignity. It's just a way not to be prosecuted by law for defamation. It's not the way to say something politely. You can say that you are confused after reading what I've written, but the only person that has right to say I'm confused is me.

By the way, why to use such statements? They bring nothing.

Anyway - the topic is too big for these forums

You are right. But it was my first post. I try to remember about it next time. Sorry.
 
  • #13
gfgts250 said:
I have started this thread in: Physics Forums > Physics > Classical Physics. I repeat: Classical Physics. And I've done this for reason. For me classical physics includes also : black body radiation, Photoelectric effect, generally everything until the year circa 1920. Quantum nature of light (it consists of some quantas) was then already known, but today's interpretation (generally: Quantum mechanics) was not born yet. It doesn't mean that i believe in "Old quantum theory" or something like that. No. The only information i need is: Light is not just a wave, it's build from some quantas. That's all.

Light being built from quanta is NOT classical physics by any means. This idea did not exist in classical physics.

gfgts250 said:
Quantum physics in not needed here, i haven't asked for this! Even if I'm wrong it would be easy to explain it without that! There is enough mess here even without quantum mechanics. If you think otherwise, please go away.

Yes, quantum optics is needed as soon as you really want to include the idea of light "build from some quantas". No, it is not easy to explain that classically. It is not even possible. We have that discussion here on a regular basis. But as you do not seem to be interested in how stuff works, but just in discussing your personal theory, I will indeed go away.

gfgts250 said:
And the second thing i said about photons is that OUTSIDE E-M wave they can be localized. I repeat: OUTSIDE - this is very important (i'm not sure if we even can speak about photon inside wave). So outside wave they have some properties of particles - we can measure its position (with some limited accuracy of course) and even direction of travel.

Photons inside and outside em waves? That does not even mean anything. Please keep in mind that we stick to accepted physics here and do not discuss personal theories.
 
  • #14
gfgts250 said:
I didn't said I'm imagining photons as little particles. I see them as the chunks of energies. I've assumed (and that's a fact) - that outside E-M wave they have PROPERTIES of particles (size, position, etc. - we can localize them).

I don't know what "outside" an EM wave even means.

But those properties apply also to those little waves (as you said you see photons). Such little wave (wave-packet?) also has to have finite length - so you have got already size.

Not really. Size is a difficult thing to talk about at the atomic level. The wave packet simply represents where a particle or photon might be, not its size. All elementary particles are considered to be point-like with zero size.

If you really want to give photon some geometrical form then yes: a small-wave is of course preferable one (also for me). It maintains properties of particle and explains some other effects. But it was not my intention to assume some shape of photons.

Photons, being a quanta of energy, cannot have a size or shape.
 
  • #15
gfgts250 said:
Let's continue with your spherical wave spreading out from a point source. Surround this source with spherical, opaque (for this wavelength) shell. There will be no E-M radiation outside it. Now drill a little holl in the shell and some single ray/beam? should appear.

Rays and beams are not real. They are merely ways of making things easier. For example, in optical design the optical system is typically analyzed by use of ray tracing. This gets you a very good approximation of how the system will work, but if you want to be completely accurate you have to calculate wave properties like diffraction, which are much more math intensive than ray tracing.

In your example an EM wave will emerge from the hole and spread out according to the principles of diffraction. The smaller the hole is with respect to the wavelength, the more the hole acts like a point source.

Now, for this ray/beam do exactly the same, what you've done for point source before. If I'm right, the result will be a circle (2D version) on a plane perpendicular to ray/beam direction. Of course, this circle will be periodically changing it's size, but currently it's not such important.

The circle will get larger as the wave propagates, if that's what you mean.

That's not all. Cut narrow slit somewhere else in the shell and second ray/beam? will escape. You know what to do. Result will be similar to the previous one. You should describe me this like, well maybe not exactly squere but something similar to an ellipse (a shape extended in one direction).

Initially the wavefront will be the shape of the slit, but as it travels further it becomes closer and closer to spherical.

And this my post all about: I suppose that in E-M radiation generated by antenna [Pic.2] could (i don't know for sure) be something what I've called: SINGLE WAVE (if exists, we should be able to see it at larger distances). I've told why i think so. And now I'm asking if anyone heard about something like that. If anyone know about some results of experiments, showing heterogeneity in intesity of radiationat at larger distances. Such heterogeneities should form some shape and this will be the shape of our single wave. What other question then about shape of E-M field can i ask? The shape will tell me what kind (if any) of relation between photons exists in source radiation.

I have no idea what a "single wave" is supposed to be unless you mean that it's a single fluctuation in the EM field. If so, then it still doesn't have any relation to the "shape" of the EM wavefront.
 
  • #16
gfgts250 said:
EXACTLY! Yes, this is exactly what I'm asking for! I mean general idea is correct.
I cannot tell because you have not said what you want to do it for.

Please ask a question.

Hint: E-M wave is nothing more then electric/magnetic field fluctuations which propagate in space.
This is incorrect. Classical EM has everything to do with electric/magnetic field fluctuations which propagate in space.

And this my post all about: I suppose that in E-M radiation generated by antenna [Pic.2] could (i don't know for sure) be something what I've called: SINGLE WAVE (if exists, we should be able to see it at larger distances).
All light can be represented as a single wave.
A wave, by definition, is any solution to the wave equation.

I think you are using the term "single wave" in a way that is non-standard.

If anyone know about some results of experiments, showing heterogeneity in intesity of radiationat at larger distances.
"Heterogeniety" is, by definition, the property of being diverse.

Indeed there are many experiments showing the diversity in the intensities of light at many different distances.

What other question then about shape of E-M field can i ask?
I cannot tell what other question you can ask because you have not asked the first question yet.

What question about the shape of EM waves are you trying to ask?

By the way, question about shape is not such abstract like you may think.
I don't know what to think - you have not asked a question yet.

The process you describe is called "mapping the crossectional intensity of the laser beam".
Nobody is disputing that it is possible to do this - we'd usually map a series of curves to get something that looks like a contour map.

You want to ask a question about this sort of map?
Please ask away.

Of course english is not my native language (it's not hard to guess that)
... There are native English speakers who write much worse than you, so I don't just assume this sort of thing. In English there is a saying: Never "assume", or you'll make an "***" out of "u" and "me".

- but I'm afraid it has nothing to do with confusion.
... there is certainly a problem with communication. You are using words with a non-standard meaning for example. That is certainly very confusing for the people trying to understand you and is the sort of thing that happens when the speaker/writer is, themselves, confused about something.

Please try to put your ideas in as simple a form as possible.
Please try to stick to standard uses of words.

I try to carefully analyse your statement You've said: "seemed to be confused" not "be confused". But why? If "confuse" is such neutral word, why to use "seem to"?
1. "confused" is not always a neutral word;
2. I did not know if you were confused or not.

This is the language politicians and lawyers are using.
You are in a scientific forum talking to scientists, not a political or legal forum. Scientifically we have to be careful to distinguish between how things seem and how they are.

You can say that you are confused after reading what I've written, but the only person that has right to say I'm confused is me.
You are wrong about that - it is also possible for someone to look like they are confused - by their actions or words.

In English, "confusion" is the state of being bewildered or unclear in one's mind about something.
An example if the use is "Mary looked about herself in confusion."

Confusion in others is a state which can be determined from observation. It is also possible for someone to be confused without realizing it - another way to say this is that they are mistaken, or that they have taken some ideas out of context or something more specific.

You are writing like someone who is unclear in their mind about the properties of EM radiation.
I allow that this may not be the case.

By the way, why to use such statements? They bring nothing.
It is supposed to tell you that you are giving the impression of being confused and offers you a chance to help correct the matter.

The way to go about convincing people you are not confused is to make clear statements ... you have been so busy trying so hard to explain your question that you keep forgetting to say what you question actually is.

It is best practice to ask your question first, then, if other people are confused, they will tell you, and you can explain for them and make your meaning clear.

Perhaps you feel you have asked a clear question?
Then please restate it for me by itself so I can see it.
 
  • #17
Cthugha said:
...I will indeed go away...

I didn't wanted to be rude. I stand by my request rather not to include topics from quantum physics (modern quantum physics if i can say so) here, but of course i should formulate my will in a different way. My fault, sorry if i offended you. I don't want you go away (i have nothing personally against you), i even hope you still will be using your knowledge to help me. But, if i may ask, let it NOT be the knowledge from an area of modern quantum physics, at least not for this thread. I truly think it's not needed here (at least not yet. And later?, Who knows? I will ask THEN).

Light being built from quanta is NOT classical physics by any means. This idea did not exist in classical physics.

Well, let me summarize how i see it:

I do not only oppose the fact light can be seen as build from some chunks/pieces, I also think it's crucial information for what i try to discuss. I fully accept and use experiment's results showing this quantum nature of light (blackbody radiation, photoelectric effect even Compton's experiment - which shows that quanta has some momentum - property of particle).​

as you can see: I'm not trying to speak about light using physical knowledge from XVI century. But... on the other hand i feel i don't need:

wave functions, probabilities, quantum entanglement, QEDs, QFTs, all of that.​

So it doesn't work like: all or nothing. The question is: Can i do that? I think it all depends on the scope of knowledge i need from QP (quantum physics) area (For example: I don't need to learn special relativity and know Lorenz transformations just too say trivial sentence like: "light is not standing but travels in space with some speed". do i?). From all QP i just really need 2 simple informations:

  1. E-M radiation is quantized - we can not take arbitrary amount of energy we want from some monochromatic E-M wave with frequency (nu) We have to take at least E = h*nu - this is a lower limit.
  2. Those chunks of energy are called quantas/photons. They have of course many interesting properties, but I'm particulary interested in one of them: they can be localized (with some limited accuracy of course) in space. We can detect their position and their direction of motion (where they comes from). It could be said they are behaving like particles - they are generally following in the direction initially given to them.
And this is all i need from QP. What theory do i need for that? You could be suprised but in my specific case, i don't need any theory. All this informaion i can get only from experiments. I can learn about quantization from Photoelectric effect experiment. And i can go to the store, buy some laboratory stuff and play with single quantas/photons. In many laboratory experiments single photons are generated so i assume I can do it too. I can also give them some direction (maybe i have no control over where excited atom releases photon, but i can filter, from previously generated set, these going where i want - it's just like small output window in laser works). The same with detection - there are many detectors which can detect single photons. By proper arrangement of those detectors in space i can determine photon's position and what was the direction of motion (i'm assuming that i know starting position). It's rather you could have some problem, trying to tell me I'm wrong with that. Since you need some experiment to do that. I my opinion (i hope this law still applies) experiment stands beyound any theory. By the way: The whole Quantum physics was born by experiment, not by theory. I'm not quite sure i can say the same for what is today called: modern quantum physics (modern interpretation of QP).

As for your statement: "This idea did not exist in classical physics". Well, everything depends what QP means to you. The most obvious approach is to assume QP as everything that has something to do with QUANTIZATION (hence the name. We can include knowledge from 1900-1920 in that) And believe me, I also THOUGHT so, but i was forced by people like you to change my mind. Since this approach has some consequences: key concept of QP in this case is just QUANTA. And until you are talking about quanta everything is OK. Then your statement is correct: indeed, classical physics is not enough. But, if you feel you can't speak about ANY (even basic ones) concepts of QP without wave function and other such things ("these forums cannot replace a thorough course in quantum optics - including the math") then it just means WAVE FUNCTION is key concept of QP form you, not QUANTA (and for unknown to me reasons you do not want to admit it). Then problem arises: where to classify knowledge from years 1900 - 1920 (maybe even up to 1930)? How people living then were able to speak about quantum physics without knowledge you are assuming essential today? Now, i hope, you understand why I've classified some aspects of QP as classical physics (i can't agree that some people are trying to change theories inpired by experimental results into experiments inspired by theories). So, no. Quantum optics is not needed if i really want to include the idea of light "build from some quantas" (this is from your previous post). This is what already Photoelectric effect told us in circa 1905 (experiment told us so, not theory).

Eventually, if it makes you happy, i can introduce division on: classical physics, quantum physics and modern quantum physics. In this case i can say I'm not interested in the last one.

In my original post I'm starting from E-M waves (classical physics) and I'm ending with E-M waves. Just in between I'm using a little bit QP, but only those things described previously. I must admit, later i metioned about things that COULD SUGGEST i want to talk about some aspects of modern QP but I've made it unintentionally. I mean, since no one understood me I've used some wrong examples and got into unneeded discussions. I regret that.

Photons inside and outside em waves? That does not even mean anything. Please keep in mind that we stick to accepted physics here and do not discuss personal theories.

Is this such abstract? It's just like free electron and electron that is bound to an atom. The same way we can have free photon (i've unnecessary used term: "photon outside") - photon distant from the other photons if you like (it reminds us particle). We can localize it - detect it's position/direction of motion. Or we can have E-M wave, which COULD BE (just could) interpreted as stream of photons. This is how LASER works - single photons are generated inside and released in bunches. So i think it could be seen like that. In this case we are not be able to localize such photons, we only would be able to speak about position of the whole wave (and only say it's build from photons). I don't consider it as my personal theory - it's obvious.
 
  • #18
A few things:

1. Classical physics and quantum physics are two different theories. The beginnings of quantum physics has its roots in the 1800's with several experiments and observations, but prior to the formulation of Quantum Mechanics in the 1920's and 1930's there was no theory that adequately described the atomic and subatomic world. The ideas put forward from about 1900 until the formulation of QM is termed the "old quantum theory" and is essentially a "stepping stone" from classical to quantum physics. Attempting to talk about EM waves must either involve photons and use a quantum theory, or it must not. One cannot talk about photons and not delve into modern quantum theories, as they are exactly what describe what a photon is and how it works. This isn't to say that we need to get into the nitty gritty details, it is simply to point out that attempting to talk about photons within the realm of classical physics is doomed to misunderstandings and confusion, as this very thread has pointed out.

2. The beginning of the 20th century had many experiments which disagreed with accepted physics. It was a time when we had a great wealth of experimental data, but no theoretical models, no theories, in which to explain them. It was only by building a mathematical theory that explained these results that moved us forward. So your claim that modern Quantum Physics was born by experiments and not theory is false. ALL scientific advances require both experiments and a theory. The biggest difference today in theoretical physics is that we have many theories but lack sufficient data to determine which one of them is correct.

3. Your understanding of EM waves, lasers, and photons is incorrect. A laser emits EM waves. Period. No one can claim that it doesn't because that is what light is, an EM wave. However, EM waves are quantized in their energy. A single photon sources emits an EM wave with an amount of energy equal to exactly one photon. Because this is still an EM wave, it will still show all the properties of waves, such as interference and diffraction. A laser does not emit a bunch of photons which happen to turn into an EM wave simply because there are a lot of them. It emits EM waves which are quantized.

Note that quantum physics does NOT do away with the idea of an EM wave. It doesn't say that EM waves are not really waves. What it does is it adds to the idea of an EM wave by including quantization of the energy as photons. See the following quote from: http://en.wikipedia.org/wiki/Photon#Wave.E2.80.93particle_duality_and_uncertainty_principles

Photons, like all quantum objects, exhibit both wave-like and particle-like properties. Their dual wave–particle nature can be difficult to visualize. The photon displays clearly wave-like phenomena such as diffraction and interference on the length scale of its wavelength. For example, a single photon passing through a double-slit experiment lands on the screen exhibiting interference phenomena but only if no measure was made on the actual slit being run across. To account for the particle interpretation that phenomenon is called probability distribution but behaves according to Maxwell's equations.[48] However, experiments confirm that the photon is not a short pulse of electromagnetic radiation; it does not spread out as it propagates, nor does it divide when it encounters a beam splitter.[49] Rather, the photon seems to be a point-like particle since it is absorbed or emitted as a whole by arbitrarily small systems, systems much smaller than its wavelength, such as an atomic nucleus (≈10−15 m across) or even the point-like electron. Nevertheless, the photon is not a point-like particle whose trajectory is shaped probabilistically by the electromagnetic field, as conceived by Einstein and others; that hypothesis was also refuted by the photon-correlation experiments cited above. According to our present understanding, the electromagnetic field itself is produced by photons, which in turn result from a local gauge symmetry and the laws of quantum field theory (see the Second quantization and Gauge boson sections below).

Also:

Both photons and material particles such as electrons create analogous interference patterns when passing through a double-slit experiment. For photons, this corresponds to the interference of a Maxwell light wave whereas, for material particles, this corresponds to the interference of the Schrödinger wave equation. Although this similarity might suggest that Maxwell's equations are simply Schrödinger's equation for photons, most physicists do not agree.[52][53] For one thing, they are mathematically different; most obviously, Schrödinger's one equation solves for a complex field, whereas Maxwell's four equations solve for real fields. More generally, the normal concept of a Schrödinger probability wave function cannot be applied to photons.[54] Being massless, they cannot be localized without being destroyed; technically, photons cannot have a position eigenstate |\mathbf{r} \rangle, and, thus, the normal Heisenberg uncertainty principle \Delta x \Delta p > h/2 does not pertain to photons. A few substitute wave functions have been suggested for the photon,[55][56][57][58] but they have not come into general use. Instead, physicists generally accept the second-quantized theory of photons described below, quantum electrodynamics, in which photons are quantized excitations of electromagnetic modes.

The key here is that the probability distribution of the photons follows Maxwell's Equations and that the theory that fully describes EM waves using a quantum theory is Quantum Electrodynamics. Per QED, you can't even talk about the path the photon takes between emission and absorption. In order to find the probability of a photon arriving at a location after emission, you must take into account ALL possible paths, not just one. So you can be sure of the source of the photon, but not the exact path it took through space to get from the source to the detector. You can't even localize the photon without destroying it, unlike other particles.

I'll say it one more time to be clear. Photons are NOT little particles. EM waves are NOT the result of many of these particles being in the same place. A single photon is just as much of an EM wave as a billion photons are.

As always, someone correct me if I'm wrong.
 
  • #19
Drakkith said:
A single photon is just as much of an EM wave as a billion photons are.

As always, someone correct me if I'm wrong.

Every EM wave can be described in terms of its modes; the photons are the quantization of the modes of the electromagnetic wave.

PS: In laser physics it is often necessary to consider the light as consisting of photons; and just as often it is necessary to ignore the photons and consider everything as electromagnetic waves. I've done experiments where both were important considerations, but at different locations within the same experiment!
 
  • #20
UltrafastPED said:
Every EM wave can be described in terms of its modes; the photons are the quantization of the modes of the electromagnetic wave.

Interesting. A quick search on the modes of an em wave linked me to the following article: http://en.wikibooks.org/wiki/Quantum_Mechanics/Waves_and_Modes
An interesting read. I had heard of modes before, but I'd never read much on them.

PS: In laser physics it is often necessary to consider the light as consisting of photons; and just as often it is necessary to ignore the photons and consider everything as electromagnetic waves. I've done experiments where both were important considerations, but at different locations within the same experiment!

This reminds me of the phrase, "Whether something is a particle or a wave depends on how you ask it".
 
  • #21
Has anyone spotted the question OP is asking? I though it may have been "does it make sense to talk about waves having an area?" or something like that - now I can't tell, and I am still unable to find an actual question or problem statement anywhere.

1st step in scientific method is to make a statement about the problem to be tackled.
I'm going to duck out until something like a proper problem statement shows up.

Cheers.
 
  • #22
I hope you read entire post, if not read at least LAST part.

Drakkith said:
Classical physics and quantum physics are two different theories...

I know they are. The question is why are you trying to put in my mouths words I've never said I've clearly stated in my previous post I don't try talk about some quantum properties using classical physics framework. I'm still using concepts from QP, I've just renamed it TEMPORARY(just changed the name) for reason (i admit, it didn't worked as i thought, so i regret that move, but still there was some logic behind this). You don't have to read what i write, but if you do, read all and carefully. I feel i have to give some more datailed explanation.

Let me explain what Quantum physics (name without any prefixes) means to me. It's a broad field of physics, it should contain: experiments, observations, hypothesis, theories (ALL theories introduced so far!) - it's like a container for specific knowledge (like a history or biology). Of course, there had to be some pretext to create such field, some foundation - in this case it was a CONCEPT of quantization. But except that there is no reason and no goal in it - just to study. This is a goal of THEORY to explain something (aswer why such quantization occurs, desribe the rules this process follows). And the OLD QP interpretation is an example of one theory and MODERN QP interpretation is an example of the other one (or i should rather say: modern QP is a set of associated theories). And the problem is that many cannot (or don't want) distinguish between: Quantum Physics (the general science) and Modern Quantum Physics (the theory, interpretation) - AND THIS IS THE THING THAT PROVOKED EVERYTHING - one theory has become synonymous to the whole field of quantum physics (It's almost not possible to say something having the word QUANTA in it, not being bombarded by terms like wave function of probability, field theories, modes etc.)

This becomes a real problem today, it prevents any constructive discussion. That's why I've tried temporary to classify some very basic concepts of quantization to classical physics (i recall you this thread is not about QP but E-M waves! All I've just needed from QP were 2 very basic facts. I was provoked to talk about details I didn't initially want to). I thought naively it would help me to get rid of people trying to "help", by bombarding me terms from some modern theories and telling me that I NEED to know them, to speak about things people spoke hundred years ago. Of course all this failed and now i have to explain myself why I've put light quantization in Classical physics. Lesson learned, next time I should just ignore such comments, try not to "by-pass" definitions for good cause and have no illusion i can stop them or explain something to those who "help".

And if you think that this is just my imaginary problem, then let me remind you a couple of facts in coherent form:

  • No one else but Albert Einstein who can be considered as one of the fathers of QP (by the way, he was awarded the Nobel Prize in Physics for his explanation of the photoelectric effect) until his death tried to "refute the accepted interpretation (Copenhagen interpretation) of quantum physics" (quotation from: http://en.wikipedia.org/wiki/Albert_Einstein).
  • You can also read in Bohr–Einstein debates: (http://en.wikipedia.org/wiki/Bohr–Einstein_debates) "The next shock came in 1926 when Max Born proposed that the mechanics was to be understood as a probability without any causal explanation. Einstein rejected this interpretation. In a 1926 letter to Max Born, Einstein wrote: I, at any rate, am convinced that He[God] does not throw dice.
  • Erwin Schrödinger (yes, the same Schrödinger who introduced Schrödinger's equation being math framework for QM) "wrote about the probability interpretation of quantum mechanics, saying: I don't like it, and I'm sorry I ever had anything to do with it." (http://en.wikipedia.org/wiki/Schroedinger) (let me remind you that probability interpretation is important part (foundation) of modern interpretation)
  • And even later Hans Bethe made QED (Quantum Electrodynamics) usufeul tool accidently just by substituting infinity into equations. Before that, others thought that different model was needed JUST BECAUSE maths was unusable (by the way, it clearly shows what modern QP in fact is: It's like a field of mathematics developed under the auspices of physics - physics is just an excuse for maths and philosophy?).

It doesn't mean that modern QP is totally usless or 100% false. It means that it is the theory in the field of science not the field of science itself. And if you invent some better theory explaining quantization you don't have to change dates in history (in 2014 QP was born). Light is quantized in EVERY theory belonging QP, hence the name (those theories differ of course, but not in this simple fact) and the light is quantized is a fact gained from experiments which have created this field of science. If it was our will, we would stay with pure wave interpretation of light, but experiments (not theory) show us we can't. Quantum physics was born by concept/idea of quantization, induced by results of experiments - there is no theory in this yet.

If there is some logic/coherence in your thinking then you should go now to Albert Einstein (let's assume he's still alive) and tell him: "Mr. Einstein by rejecting modern QP interpretation You are not allowed to talk about photons/quantas, quantization of light (and a couple of other things). Since it's not You (one of) who 100 years ago have discovered them, it's modern QP has created them. You really have to learn about it. Modern QP is very good it explains everything. That's a fact - Wikipedia and people on forums told us so."

Is this what you going to do? If not, then let me do what you allow do Einstein (by the way, Einstein wanted to explain something, i don't even need that, i want to say one basic sentence). I repeat one more time: i DON'T NEED any theory just to know light IS somehow quantized (i need one if i want to know WHY and HOW).

One cannot talk about photons and not delve into modern quantum theories, as they are exactly what describe what a photon is and how it works.

Except everything what was said above, let me add to this that it doesn't work as you may think: because of Einstein rejected newer interpretation it wasn't mean he still belived and used the old one. Physics is physics it works like it works, we people are still trying to figure out how and for this we are creating some theories. If some theory fails it doesn't mean universe collapse. A new theory in not correct just because an old one failed or no one invented something better. Modern QP interpretation is not very impressive as many think. It still doesn't explain much (it depend on you if you aknowledge as an "explanation" theory assuming some virtual particles we never will be able to discover and we just have to believe they act like theory says). You are very wrong about that: absolutely no theory today explains exactly what a photon is and how it works - but of course, many will be trying to tell you so (modern interpretation is used today not because it explains everything but because no one can invent something better).

Don't forget that all science (and QP is one of it's fields) is today a huge employer giving work to thousands of people. Physics is their job, they get paid for it - they life depends on it. Not all have good intentions, many of them are trying to advertise some areas of science and researches "accidentally" they are working on, of course trying to "help" (on thread created for me). I don't think you're one of them but ufortunately reading your answers, sometimes I'm not quite sure if you're aware of that (aware of people motives). You will stuck forever in front of your computer reading about such theories, driven by conviction that everything is already known and now all you have to do is just to read about it. Those people are trying exploit it (sometimes with the help on naive ones) - for their own purpose (by giving "help" - they gain the audience nedded for their researches or fields of science they are working on). Today, you really have to have some good FILTER to find out something from physics - and this is exactly what I'm trying to do: keep everything unneeded out of my thread. And you are not helping me in this, really.

theory that fully describes EM waves using a quantum theory is Quantum Electrodynamics

One detail: "...that fully describes ... using a MODERN quantum theory..." (well, could be). But it's better for me. You have at least half of the century with ligth (photons) and without modern theory explaining it (old was abandoned in circa 1920 - so you have a hole between 1920-1950). It had to be very hard keep your mouths closed for such a long time, since: "One cannot talk about photons and not delve into modern quantum theories". And if QM is 80% math, QED is 95% math + some virtual particles - of course probability is in both of them.

Note that quantum physics does NOT do away with the idea of an EM wave.

You are still trying to put my mouths words I've never said. This is just YOUR annoying conviction I've pure particle model of light in my mind. How can i speak about some particle properties not using word "particle"? It's rather you don't know how to combine particle properties with wave ones and still trying to describe everything with waves. "Wave-particle duality" tells all - the question is what word "particle" means to you?

... you can't even talk about the path the photon takes between emission and absorption ...
... In order to find the probability of a photon arriving at a location after emission, you must take into account ALL possible paths, not just one So you can be sure of the source of the photon, but not the exact path it took through space to get from the source to the detector...

You have very, very wrong conception about photons - and i even know where it comes from. One link is worth more then 1000 words - this is description of real life experiment performed many times and is continued even today:

http://science.nasa.gov/science-news/science-at-nasa/2004/21jul_llr/

"In 1969 astronauts put on the surface of moon the so called: lunar laser ranging retroreflector array - wide panel studded with 100 mirrors pointing at Earth. Using these mirrors they can 'ping' the moon with laser pulses and measure the Earth-moon distance very precisely. This is a wonderful way to learn about the moon's orbit and to test theories of gravity. Here's how it works: A laser pulse shoots out of a telescope on Earth, crosses the Earth-moon divide, and hits the array. Because the mirrors are corner-cube reflectors, they send the pulse straight back where it came from. Back on Earth, telescopes intercept the returning pulse - usually just a SINGLE PHOTON, The round-trip travel time pinpoints the moon's distance with staggering precision: better than a few centimeters out of 385,000 km."

Let me explain it to you:
Time is the only parameter we are measuring. Speed of the light is already known. So, the only way to calculate this distance with such a precision is to: VERY PRECISELY KNOW THE PATH photon will follow. And this path is: STRAIGT LINE. This is exactly how photon in real life behaves! (of course a single photon appears only in the final section of the trip, but hundreds/thousands of km are more then enough to see the principle) As you can see it doesn't have much to do with this what you have quoted. How can you imagine this? Photon is going sometimes to the Earth taking straight line and the other time it goes to the Mars and then to earth? It is not possible -the distance between Earth and Mars (one of the closest planet) is milions of km (it takes over 3 s for light to travel 1 million km, and about 2.5 s to ping the moon). Assuming precision of a few cm, path can't differs in length more then: 10 cm (0,0001 km) / 400 000 km = 0.000 000 000 25 km (250 nano meters) per 1 km. And, of course, it's a worst case - those few cm are rather effect of limited precision of time measurement then real deviation.

Now the harder part. Trying to explain you, where your misunderstanding comes from.

"you can't even talk about the path the photon takes between emission and absorption"

As you were able to see, this quotation is not universal description of photon behaviour - it has nothing to do with reality. It was taken completely out of context from: a) some modern theory (probably QED) or b) some experiment (probably double slit experiment with single photon).

In modern theories (like QED) there are many of such concepts like virtual particles or something like that. Those particles spontaneously appears (are emitted) then immediately dissapears (are absorbed) - everything of course in period of time and at scale we will never be able to measure. So, such quotation could be just description of such virtual,instant process which can proceed however it's original inventor/"discoverer" imagined.

In the double slit experiment (with single photon) - the only thing we can be sure is: when we shoot one photon toward the double slit barrier interference pattern will appear on the other side. Photon going through both holes in the same time with some probability is just the INTERPRETATION of such phenomenon. Interpretation which if tranferred to real life, to macro scale becomes an ABSURD. That's why there have to be some conditions, exceptions included in this interpretation (you forgot to mention), like: everything happens at limited sizes and distances (quantum scale) or something like that. (we still really don't know how photon and other particles are build. whether actually photon can not be somehow divided. or forgetting that there is some matter between slits with which photon can/have to interact/collide - we don't really know if exiting photon/photons is/are the same as incoming or it's just a newer one/ones generated as a result of some interactions). So, what you have quoted is currently accepted INTERPRETATION for this specific situatinon/experiment - not some general law.

If you think I'm wrong, you should go to the NASA and tell them: "All your measurements are wrong since you can't even talk about the path the photon takes between emission and absorption. You must take into account ALL possible paths..." Is this what you going to do? If not, stop teaching others about what you have no coherent knowledge about.



That's all for now, you are wrong in many other points (except photons there are also laser, rays, EM waves) - it's not surprise since photon is denominator in those ideas. But it's waste of my time to talk about everything. i want see first how you react to this (don't forget this thread was created for me/to help me - not to talk about strange concept of photon you have). You've probably wanted to convince me to some today's theories, unfortunately so far you are doing something exactly opposite.
 
  • #23
gfgts250 said:
or can recall any knowledge/facts I've missed?

You have ignored (a) diffraction effects, and (b) bandwidth.

My questions for you:

a. Have you taken a course in optics?
Reason for question: all of this should have been covered in a course devoted to optics, and the effects should be obvious from the lab sessions.


b. Have you taken a course in quantum mechanics?
Reason for question: QM courses teach how to do calculations; if the calculations match the experimental results - well, then the theory (e.g., non-relativistic QM, circa 1926) works for that situation. As the entire realm of effects is studied, experiments reveal that (i) relativity must be included [Dirac 1928 or so], and (ii) the "second quantization" (of the classical potentials) must be carried out [between 1932 and 1948]; this process ultimately yielded quantum electrodynamics (QED), which is our most accurate calculational tool.

QED is usually a graduate level course, and requires quite a bit of prior experience with ordinary QM, and lots of math - though it is possible to learn it on your own, with patience and fortitude.

c. Why are you "asking questions" in the form of an argument?
Reason for question: your presentation is argumentative, with extensive discursions from any definite question. For example, what is your goal? Is it to show us how little we know about how theoretical and experimental physics is/should be done? Or is to show us the error of our ways? Are you attempting to learn something, or are you attempting to teach us something?


You can check my profile for my background; I'm as transparent as a decent piece of glass: some wavelengths make it through, others are absorbed, and some of the light is reflected, perhaps illuminating some other point.
 
  • #24
gfgts250 said:
I know they are. The question is why are you trying to put in my mouths words I've never said I've clearly stated in my previous post I don't try talk about some quantum properties using classical physics framework.

Your intentions and what you've written in your posts do not match. For example, from an earlier post of yours:

Now we've got our photons, but one question remains: how are they arranged relative to each other? Are they spread uniformly, or maybe there are some centers around which they accumulate? It's worth to remember, there was specific reason why photons moved away from each other: Their initial vectors of momentum were different (photon can be treated as a particle, it can have momentum) - their directions were different (this is characteristic feature of spherical wave. For E-M waves generated by laser this phenomenon is not as visible - laser ray can travel longer distances without energy dispersion).

Talking about quantum properties in a classical framework is exactly what you are doing.

And the problem is that many cannot (or don't want) distinguish between: Quantum Physics (the general science) and Modern Quantum Physics (the theory, interpretation) - AND THIS IS THE THING THAT PROVOKED EVERYTHING - one theory has become synonymous to the whole field of quantum physics (It's almost not possible to say something having the word QUANTA in it, not being bombarded by terms like wave function of probability, field theories, modes etc.)

Yes, that's because those are the theories that accurately explain the subatomic scale and they use those concepts. There are no other theories that match observations and don't use them.

This becomes a real problem today, it prevents any constructive discussion. That's why I've tried temporary to classify some very basic concepts of quantization to classical physics (i recall you this thread is not about QP but E-M waves! All I've just needed from QP were 2 very basic facts. I was provoked to talk about details I didn't initially want to). I thought naively it would help me to get rid of people trying to "help", by bombarding me terms from some modern theories and telling me that I NEED to know them, to speak about things people spoke hundred years ago. Of course all this failed and now i have to explain myself why I've put light quantization in Classical physics.

The problem is that you cannot put quantization in classical physics. It leads to people trying to think of EM waves as photons moving through space like little particles that somehow add up to form an EM wave.

And if you think that this is just my imaginary problem, then let me remind you a couple of facts in coherent form:

Just because some highly popular scientists don't like how Quantum Mechanics is interpreted doesn't mean much here on PF. We deal with how current, mainstream physics is explained. Not about whether or not the explanation is liked.


[*]And even later Hans Bethe made QED (Quantum Electrodynamics) usufeul tool accidently just by substituting infinity into equations. Before that, others thought that different model was needed JUST BECAUSE maths was unusable (by the way, it clearly shows what modern QP in fact is: It's like a field of mathematics developed under the auspices of physics - physics is just an excuse for maths and philosophy?).

This clearly shows your biased opinion and misunderstandings. Modern theories are in use because they work. They accurately describe the world around us, despite the fact that they don't always seem to mesh well with our normal way of looking at the world and are often underpinned by complex, abstract mathematics.

Light is quantized in EVERY theory belonging QP, hence the name (those theories differ of course, but not in this simple fact) and the light is quantized is a fact gained from experiments which have created this field of science. If it was our will, we would stay with pure wave interpretation of light, but experiments (not theory) show us we can't. Quantum physics was born by concept/idea of quantization, induced by results of experiments - there is no theory in this yet.

All accepted theories have to explain experimental results. So what?

If there is some logic/coherence in your thinking then you should go now to Albert Einstein (let's assume he's still alive) and tell him: "Mr. Einstein by rejecting modern QP interpretation You are not allowed to talk about photons/quantas, quantization of light (and a couple of other things). Since it's not You (one of) who 100 years ago have discovered them, it's modern QP has created them. You really have to learn about it. Modern QP is very good it explains everything. That's a fact - Wikipedia and people on forums told us so."

This is incorrect. The interpretation of the theory is not the same as the theory itself. There are multiple interpretations of Quantum Mechanics, but they all make the exact same predictions using the same theory. The interpretations simply differ in how they explain what various aspects of the theory, such as wave-function collapse, mean. Einstein, along with many other since him, have been bothered by QM since it doesn't always seem to match our pre-conceived ideas of how the universe should work.

Physics is physics it works like it works, we people are still trying to figure out how and for this we are creating some theories. If some theory fails it doesn't mean universe collapse. A new theory in not correct just because an old one failed or no one invented something better. Modern QP interpretation is not very impressive as many think. It still doesn't explain much (it depend on you if you aknowledge as an "explanation" theory assuming some virtual particles we never will be able to discover and we just have to believe they act like theory says). You are very wrong about that: absolutely no theory today explains exactly what a photon is and how it works - but of course, many will be trying to tell you so (modern interpretation is used today not because it explains everything but because no one can invent something better).

A theory is correct because it makes accurate predictions, something which modern theories do extremely well. They are replaced by newer theories whenever the newer theory makes more accurate predictions. Whether or not you believe that modern theories "explain" what a photon is, is your personal opinion.

Don't forget that all science (and QP is one of it's fields) is today a huge employer giving work to thousands of people. Physics is their job, they get paid for it - they life depends on it. Not all have good intentions, many of them are trying to advertise some areas of science and researches "accidentally" they are working on, of course trying to "help" (on thread created for me). I don't think you're one of them but ufortunately reading your answers, sometimes I'm not quite sure if you're aware of that (aware of people motives). You will stuck forever in front of your computer reading about such theories, driven by conviction that everything is already known and now all you have to do is just to read about it. Those people are trying exploit it (sometimes with the help on naive ones) - for their own purpose (by giving "help" - they gain the audience nedded for their researches or fields of science they are working on). Today, you really have to have some good FILTER to find out something from physics - and this is exactly what I'm trying to do: keep everything unneeded out of my thread. And you are not helping me in this, really.

This is pure nonsense. Simple as that.



You are still trying to put my mouths words I've never said. This is just YOUR annoying conviction I've pure particle model of light in my mind. How can i speak about some particle properties not using word "particle"? It's rather you don't know how to combine particle properties with wave ones and still trying to describe everything with waves. "Wave-particle duality" tells all - the question is what word "particle" means to you?

Your posts speak for themselves. You are trying to put together particles and waves in a manner which does not work. Instead, you should realize that scientists already figured out how to combine the two in a way that allows us to make accurate predictions.

Let me explain it to you:
Time is the only parameter we are measuring. Speed of the light is already known. So, the only way to calculate this distance with such a precision is to: VERY PRECISELY KNOW THE PATH photon will follow. And this path is: STRAIGT LINE. This is exactly how photon in real life behaves!

I don't believe this is correct. There is no way to know where the photon is prior to measurement or what exact path it took between emission and absorption. See here: http://en.wikibooks.org/wiki/A-level_Physics_(Advancing_Physics)/Quantum_Behaviour

In the double slit experiment (with single photon) - the only thing we can be sure is: when we shoot one photon toward the double slit barrier interference pattern will appear on the other side. Photon going through both holes in the same time with some probability is just the INTERPRETATION of such phenomenon. Interpretation which if tranferred to real life, to macro scale becomes an ABSURD. That's why there have to be some conditions, exceptions included in this interpretation (you forgot to mention), like: everything happens at limited sizes and distances (quantum scale) or something like that. (we still really don't know how photon and other particles are build. whether actually photon can not be somehow divided. or forgetting that there is some matter between slits with which photon can/have to interact/collide - we don't really know if exiting photon/photons is/are the same as incoming or it's just a newer one/ones generated as a result of some interactions). So, what you have quoted is currently accepted INTERPRETATION for this specific situatinon/experiment - not some general law.

Science isn't in the business of being absolutely sure about things. The modern way of explaining the double slit experiment works extremely well, whether you like it or not. Also, the "interpretation" works just fine when scaled to macro scales since it also explains the reason we can't walk through two doors at once. (The reason being that the wavelength of something scales inversely with the mass/momentum)

That's all for now, you are wrong in many other points (except photons there are also laser, rays, EM waves) - it's not surprise since photon is denominator in those ideas. But it's waste of my time to talk about everything. i want see first how you react to this (don't forget this thread was created for me/to help me - not to talk about strange concept of photon you have). You've probably wanted to convince me to some today's theories, unfortunately so far you are doing something exactly opposite.

Coming to a science forum which discusses mainstream theories, and then accusing those who try to help you of not knowing those same theories, is a little counterproductive. Instead of accusing me of not knowing my science, you should consider asking how the explanations I give match up with experiments. In other words, you should ask how the theories lead to real life observable effects like being able to measure a photon's flight time from the emission source to the detector.
 
  • #25
Read all, but if you really don't have to, answer only to last part.

UltrafastPED said:
...the effects should be obvious from the lab sessions...

Rhetorical questions: What effects? Do you even know what I'm talking about, what this thread is about?

All i want to ask is described in my first post. If you can understand my first post (just understand what i want to say, not necessarily agree), you don't have to read the rest and maybe even you shoudn't do it (at least before understanding the first part) since you are interpreting things out of context. It doesn't mean, of course, i deny what I've said - we can talk about everything what has been written - but some order in the discussion has to be preserved. So, for now, let's focus ONLY on the KEY CONCEPT included in the main post.

Why are you "asking questions" in the form of an argument?

My first post is question in the form of description of phenomenon - i was expecting some constructive comments. Especially i was hoping someone directs me to some experiments or researches describing something similar to what I've presented. Now i see it was rather naive thinking. Nothing is for free - even help, so it's no surprise some strange people have appeared (people with different motives, from those who are trying to "advertise" to those who want to show the world what they've learned yesterday reading wikipedia, present some "smart" saying or something like that - of course everything in the form of "help") and now are trying to talk/teach about things I've never asked. And if I've never asked about them means that i can have some knowledge about it. Add to this the fact that these people do not necessarily have the knowledge just because they have more posts in statistics then me - and now you've got the answer to your question.

Others started this, not me. And even you are now doing the same, too! Do you know what the main question is? I doubt. That's not problem yet, since no one has understood me so far (maybe even it's my fault). The real problem is while blaming me for lack of question in my thread, you are trying to "answer this question" at the same time: "...You have ignored (a) diffraction effects, and (b) bandwidth...". Is there any logic in this?

You can check my profile for my background; I'm as transparent as a decent piece of glass: some wavelengths make it through, others are absorbed, and some of the light is reflected, perhaps illuminating some other point.

Should i laugh or cry? If you think my some previous statements about motives of people answering me applies to you - you are wrong. It was (so far) about previous poster(s).

a.Have you taken a course in optics?
b.Have you taken a course in quantum mechanics?

This time i just ignore those "questions". But don't worry, i promise i will give you some opportunity to show your knowledge - the condition required to ask such "questions". Now seriously: maybe a little bit precision in problem's formulation from my side and a little bit good will for understanding from your side will be enough to avoid such comments.

Honestly i have to admit the FORM (just form) I've introduced this key concept was a little bit, well... not optimal. I tried to say too much at the same time. I unnecessarily continued description, rather than to make sure that everyone understands what was said so far. I started to talk about consequences (shape of E-M wave and methods to measure it) before i sufficiently described the reason. All of this has introduced a little bit mess, the discussion moved on to other topics, some people joined it and still trying to explain things i think they don't understand or things about which I've never asked. So, it's best time to change the strategy: I'm starting to present entire problem one more time. But this time i will do this step by step. Below is step #1. Forget about everything else (i mean other posts. just for a moment - we can go back to them later) and comment only this one.

Here is the main problem - the key concept behind all this thread (main motive):

  1. Energy carried by electromagnetic radiation generated by point source covers bigger and bigger area with the distance from the source. This effect could be easily visualized using ripples on the water as an example. When you touch water surface with your finger, you will see a circle. The circle with time will grow bigger, but since it carries some determined amount of energy, it's amplitude decreases - the circle becomes larger but less visible. So, back to our E-M radiation: wavefront will be sphere, with radius proportional to time elapsed. But since wavefront carries the same amount of energy all the time, density of energy per unit area of such sphere has to be smaller with bigger radius. Knowing power of the source, we can arbitrally assume/choose some specific energy density and then calculate distance from the source where such energy density appears. In pure wave model of light there is nothing special with it. Energy passing through some unitary area depends on it's distance from the the source and covers such area uniformly.

  2. But if we realize the fact light is quantized (by the way, it is the ONLY information i need from Quantum Physics: just the fact light is somehow quantized, doesn't matter how and why), we get interesting situation. Substituting for area some measurable quantity (for example: 1m^2) and energy of single photon for energy, we can calculate density of energy for such values. Then we can estimate the distance from the source where such density of energy is present. And this in turn allows us to formulate very important conclusion:

    At this distance from the source we should be able see: at least single photons with avarage distance from each other equal to 1m (we can't take single photon and spread it uniformly over area of 1m^2 - this is obvious consequence of quantization) or maybe even more interesting their arrangement... (but that's enough for now, i don't want to continue not being sure if what I said has been understood)​

Now, my ONLY question for you: Is that clear? Can we agree at least on what has been said (points: 1 and 2)? I so, we can proceed further, if not we have to clarify this. Agree or show what is wrong but don't talk about anything else.
 
  • #26
gfgts250 said:
Now, my ONLY question for you: Is that clear? Can we agree at least on what has been said (points: 1 and 2)? I so, we can proceed further, if not we have to clarify this. Agree or show what is wrong but don't talk about anything else.

You write way too much ...

I have a PhD with a specialty in laser physics - please ask nice, simple, one-at-a-time questions.
 
  • #27
gfgts250 said:
(1) Energy carried by electromagnetic radiation generated by point source covers bigger and bigger area with the distance from the source...
... you mean that the flux from a point source decreases in proportion to the square of the distance from the source?

But if we realize the fact light is quantized (by the way, it is the ONLY information i need from Quantum Physics: just the fact light is somehow quantized, doesn't matter how and why),
Unfortunately the how and why is important to the conclusions you are attempting to draw so you cannot get anywhere from that position.

The photon flux decreases with distance from a point source in proportion to the square of that distance. It follows that there must be some distance where a given ideal photon detector will only register discrete detection events - individual counts of photons. Like the clicks in a Geiger counter - particle-like events.

An array of detectors would also give you a spatial distribution.
You can measure the distance between two detections but it is more probematic to assign a distance between two photons before they are detected.

Now, my ONLY question for you: Is that clear? Can we agree at least on what has been said (points: 1 and 2)? I so, we can proceed further, if not we have to clarify this. Agree or show what is wrong but don't talk about anything else.
You will discover that when you ask for free-of-charge assistance, people will talk about whatever they think is in your best interests to talk about.

What you have written is a very pop-sciencey way of describing particle physics in relation to classical wave theory. You have been repeatedly told this is not a good way to go forward as it is almost certain that your problem is related to a misunderstanding this approach tends to produce.

You have been repeatedly asked for a clear problem statement, that and you have repeatedly ignored that request. If you do not come up wit a problem statement, we cannot help you.
Please stop beating around the bush.
 
  • #28
Drakkith said:
Also, the "interpretation" works just fine when scaled to macro scales since it also explains the reason we can't walk through two doors at once. (The reason being that the wavelength of something scales inversely with the mass/momentum)

Not "wavelength of something" but "wavelength of moving particle". Do you have any idea what you are quoting? It was taken (directly or indirectly) from the de Broglie hypothesis about wave proprties of particles (hence mass appears). According to this hypothesis every moving particle has also properties of wave, that's why in double slit experiment we can observe interference pattern not only for photons but also for small particles. Wavelength of particle is inversely proportional to it's mass (greater mass = shorter wavelength/higher frequency). Diffraction (and double slit experiment depends on this effect) is generally best observable when wevelength is comparable to slit size. And that's why, IF we are talking about particles, diffraction is only visible for small ones, like electrons, neutrons, atoms. For macroscopic objects, wavelength is so short that we can/have to completely ignore it (forget about wave properties).

What does this have to do with my example with "pinging" the moon? NOTHING!

  1. I my example we are using photons not particles. So why to even mention about properties of particles? Photon doesn't have mass (at least we are assuming so). De Broglie hypothesis doesn't apply to it.
  2. Term "macro scales" can mean everything. We have to define first what. For original author of sentence you've quoted "macro scales" means particles with macro size/mass. In my example, in both cases (laboratory slits, moon) THE SAME photon is used. Term "macro scale" has nothing to do with properties of test particle, it's rather DISTANCE photon travels. With such long distances we can clearly see (and even verify experimentally) REAL consequences of so called: multipath interpretation.
  3. (*)This is an optional/additional argument. Even if we were talking about particles (but we are not) then wavelength dependence from mass explains why we don't observe wave behaviour (effects) for large particles, not that "multipath interpretation" is true (it is overinterpretation). It's like saying: "USA has the largest GDP (Gross domestic product) in the world, it's the best country to live". And then quoting data confirming GDP as the proof to the whole sentence (second sentence from your quotation is true, first no so much). Double slit experiment ONLY shows us the interference had happened, not WHY it happened! And de Broglie hypothesis only explain us why we can't see some wave effects for heavy objects - it's not an argument for "multipath interpretation".
All of this shows that you don't understand the problem, you are quoting sentences out of context just because they have similar words (double slit, wavelength, macroscale) and you are thinking it's the explanation. We are talking about different things.

I don't believe this is correct.

That's all? I'm giving you a perfect opportunity to demonstrate me how modern QP explains things. I'm truly very interested how it is possible to draw different path without changing duration of the event or speed of the light.

Any deviation from straight line will manifest itself in longer travel time of photon. We can't see it in laboratory doing double slit experiment since distance is too short (in comparison to speed of the light) - we don't even have equipment to perform such measurements with sufficient precision. And such non verifiability of phenomenon is the main reason why "multipath interpretation" can "work".

We should be able to test it when distance is long enough. Do you have any experimental data showing that light/photon travels from point A to pont B in longer time than it can be calculated knowing speed of the light? If no, then you have no choice other than accept fact the path is straight line or add to "theory explaining everything" yet another assumption that: photon following different path can do it with speed higher than speed of light.


All this "explanation" fails if you realize speed in universe is limited by speed of the light. Every path takes different time. We would have to wait almost ten years for part of photon going via Alpha Centauri (about 5 years in each direction). But if photon can go via Alpha Centauri why not other stars? These hundred, thousand, million or billion light years from the earth. Photon detectors (devices we already have) wouldn't work - we would be waiting FOREVER and all the time detector has to be turned on to register photon's parts arriving from different paths. And if we can register photon without part of it (even extremally small), it means photon can be divided - it can't be called quanta. We HAVE TO exceed speed of the light for such nonsenses to be consistent with everyday life experience. This "explanation" undermines almost every law of physics! Photons can exist everywhere, at any time, can travel with infinite speed, "don't behave the way we would expect them to", they are intelligent (know where the observer is, where to return) - it should be no surprise that making such assumptions we can "explain" absolutely anything. It's like: give me $1000 and i will give you "free" present worth 10 bucks. This is not explanation, this is MANIPULATION. Made for reasons you deigned to summarize: "This is pure nonsense. Simple as that".

I've criticized you for bringing here topics from physics of particles, but maybe it was not such a bad idea - you've answered yourself in some sense. We can observe exactly the same effect for photon and electron in double slit experiment. Does your explanation apply also for electrons? If not, why do we have to use it for photons? If yes, well... Does electron fired from electron gun in your old TV (CRT) have to go to Alpha Centauri before reaching fluorescent screen at the front? Can we even call an electron particle (if, in your opinion, we cannot say photon has some properties of particle)? If not, are there any elementary particles you know (because, in theory, all known today should do what photon can in double slit experiment)? And because everything is build from elementary particles... it is not even worth further comment.

By the way, what sources you are using? "Wikibooks: the open-content textbooks collection that anyone can edit". If anyone, then could be even i. Who knows, maybe I've written this chapter just for fun, and now I'm laughing at those who believe in such things. You can (and today even have to) use such sources to quote some facts (names, dates, values), short, secondary problems but not fundamental decription of the idea.

There is one thing positive in showing me this source where your knowledge comes from: "We also know that photons aren't waves or particles in the traditional sense of either word." Is this THE SENTENCE inspiring you to constantly paralyze all the discussion whenever i use word: particle? The way you are interpreting this sentence doesn't have any sense. "...aren't waves or particles in the traditional sense..." means rather they are not solely one of them, not they aren't any of them. What terms like: "wave-particle duality" mean to you ? If we can't use any properties of particles why even include word "particle" in this term which applies (this term) to photons too? If all your knowledge is accumulated in this one sentence, maybe just another one (from encyclopedia also "anyone can edit") can cancel it: "(photon) ... also act as a particle giving a definite result when its position is measured." [Source: FIRST paragraph of http://en.wikipedia.org/wiki/Photon] - so exactly what i need and said it before.

Sorry but i can't resist and i need to add a few words about "little" which also appeared together with word "position". This is from your post #14: "The wave packet simply represents where a particle or photon might be, not its size." Do you know that probability wave in QM is synonymous to position in classical mechanics? It applies to every particle (electron, proton, etc.). And EXCEPT this photon should be also carrier of elementary E-M field fluctuations (because many of them added together create measurable E-M field changes called E-M wave - see as a proof next part of this post) best described by wave function (that's why just QED "explains" photon, not QM). So we have at least two waves here (*): one represents placement in space of E-M elementary fluctuations and the second one describes such fluctuations themself. And, as you should know, field (for example electric) is continuous - it can't just drop instantly to 0 at some point, it has to do it gradualy - so here is the argument for photon size.

"All elementary particles are considered to be point-like with zero size". Are you sure photon has zero mass or charge? We just assuming so - see [http://en.wikipedia.org/wiki/Photon - frame on the right]. Mass: 0 < 1 x 10^-18 eV/c^2, electric charge: 0 < 10^-35 e. The same applies for size - but this information has been placed implicitly in the frame (word: "elementary particle" was used). Range of size should be found somewhere in definition of elementary particle. Upper limit should be Plank's length or something like that. No one can assure you that photon has 0 size (it's just assumption made for calculations) - you can't read such statements.

(*) - this is good example how many followers "understand" modern QP. They confuse position expressed as a wave of probability with other wave properties - just because word "wave" is used.

But the most important thing in all of this is: Do you know what is MOST ESSENTIAL in modern QP interpretation? That this wave of probability is particle itself, in other words: NO "where a particle or photon MIGHT be" but where it IS at the same time (interpretation where particle/photon is exactly somewhere in space, in one point but we can't measure it precisely so we just are using some mathematical function of probability to approximate calculations - is CLASSICAL interpretation - this way you can't explain double slit results and tunelling effect). This is THE CORE of modern QP interpretation (by the way, this is what Einstein resisted. He thought: math is ok, we can do calculations with it but it's not explanation itself, there must be something behind all this math)! And you even said it yourself (i mean that photon is everywhere) - giving me link to description of photon following many paths. The problem (problem for you, not me) is this interpretation stays in TOTAL opposition to your previous explanation: elementary particle without size. Because in your last interpretation photon has in fact infinite size (...going via Alpha Centauri...). "You can't have your cake and eat it", so decide: has photon 0 size or is it going via Alpha Centauri? If i may suggest: stay with 1st case but add word "almost" and forget about "multipath interpretation".​

"...think of EM waves as photons moving through space like little particles that somehow add up to form an EM wave."

Do you know how does the laser operate? For example: gas laser uses as a gain medium some gas which (like everything) consists of single molecules/atoms. Each atom has electrons. When (in excited atom) electron returns to lower energy level a single photon is generated. This is exactly what atom can do: generate a single photon - not a continuous wave. And because there are many such atoms in laser, stream of photons is generated which we used to call: E-M wave! So YES, the E-M wave from laser is created by add up of single photons (which, by the way, have some properties of particles, the most interesting for us is: position in space).

But AFTER the "add up", their E-M fields (in fact this is what photon is) will overlap and we will lose ability to determine position of each of them (photons are bosons, can exist in the same place in the same time - we won't be able to distinguish one from the other). From now, the only way we can describe their cumulative movement is to use some general/mathematiacal/statistical methods and it turns out the best method is to use concept of... WAVE (classical wave). So we are USING (*) "mathematical wave eqution" to do some calculations and predictions that's why (after "add up") we used to call it wave. But is this wave a new (one) independent entity or is it still a group of photons just well described by wave equation? The best, general explanation i can give is: Starting from separate drops of water we can form a puddle by adding one drop to the the other. But is puddle a set of drops or entirely new entity? Well, it's rather formal/philosophical question.

We also would be able to invert entire process. For our example with puddle we can put finger into it then pull out and at least one water drop should stick to it. This way we can divide all puddle into separate water drops. But are those drops the same ones which previously formed the puddle? Which is which? It's the same dilemma as before... but at least we will be able again to localize in space separate drops. The same process not only can occur for E-M radiaton but also it occurs naturally/spontaneously (not like removing drops from puddle by external factor). And THIS is exactly what I've tried to show by all the time: that at specific distance from the source of radiation at least separate photons should appear (and probably one person finally understood at least that - check post #27).

Conclusion: E-M radiation can be created from separate photons and in specific conditions can be decomposed (or rather should decompose itself) into photons. Between... we don't know how to treat them but we know how to describe them - using wave equation.

(*) - before discovery of photon it was assumed that light really behaves like ideal wave but it turned out that not - so mathematical model of wave and reality describe by it are no longer always synonymous. In the majority of cases approximation works almost perfectly but in specific situations when energy of E-M wave starts to approach energy of photon (and this is EXACTLY the case I'm trying to analyse - most readers constantly omit this "detail") wave model from textbook can't be used. So don't (THIS IS MESSAGE TO ALL OF YOU) tell/teach me about laws of optics (they apply to ideal waves - mathemathical model) not knowing exactly what I'm talking about.​

Just because some highly popular scientists don't like how Quantum Mechanics is interpreted doesn't mean much here on PF. We deal with how current, mainstream physics is explained. Not about whether or not the explanation is liked.

What do you mean saying: "doesn't mean much here on PF"? Are you authorized to speak in the name of every member? All you can say is: it doesn't mean much to you. Well, I'm accepting this information. I hope you will accept my: state of mind of the mass/majority doesn't mean much for me. Because this is exactly what you mean (consciously or not), saying: "how current, mainstream physics is explained".

"Not about whether or not the explanation is liked" - well, but do you realize that "mainstream physics is explained" means exactly nothing more than "most like this explanation"? And "like" means "feel it explains" for each of them. What are you trying to suggest? That Einstein (and some others) used his intuition against some obvious, confirmed facts?

"In 1926 Max Born (almost as popular as Einstein scientist) proposed that the mechanics was to be understood as a probability without any causal explanation" http://en.wikipedia.org/wiki/Bohr–Einstein_debates - just because he liked it. And Einstein opposed - because he doesn't like it. This is how base of today's interpretation was born, not by some landmark discovery. "Confirmation" came later and has grown proportional to number of researches employed in this field.

I don't use opinion of Einstein (his authority) as an argument that modern QP interpretatation is wrong (i'm trying to show doubts in another way: see above), but it is very useful to silence people trying to use not scientific informations but rather their scientific degrees, statistical data about acceptance of something or number of posts in their profile as an argument.

By the way, it seems to me you must be kidding ignoring on the one hand opinions of some popular scientists, data from some experiments and on the other hand taking single sentences from anonymously edited sources as revealed truth you are ready to die for.
 
  • #29
UltrafastPED said:
please ask one-at-a-time questions

Is this possible to explain such things like "multipath interpretation" (interpretation where: photon follows many paths - i guess essential to modern QP) without exceeding speed of the light (*)? I'm asking because photon or "part" of it following different path than straight line has to do it with higher speed to reach the destination in specific (or for some paths even finite) time?

(*) - if you need reason or context of question read post #28 (my last post to Drakkith), parts 2 and/or 3 (first 2 paragraphs).

... ask nice...

Do you mean: "Is that clear?" or "don't talk about anything else"?

English is not my native language. I know the words at acceptable level(i think so) but (must admit) don't always feel the "strength" of sentences. It wasn't my intention to give you an orders. By the way, it was also addressed to the others not only for you. If i was unpleasent: sorry.

I have a PhD with a specialty in laser physics.

Congratulations but is this an argument?
 
  • #30
Simon Bridge said:
The photon flux decreases with distance from a point source in proportion to the square of that distance. It follows that there must be some distance where a given ideal photon detector will only register discrete detection events - individual counts of photons. Like the clicks in a Geiger counter - particle-like events. An array of detectors would also give you a spatial distribution. You can measure the distance between two detections...

I'm not quite sure but it seems to me we finally almost understood each other (by the way, I'm very interested if I had used such words in my first post, did you understood me immediately). Maybe, except this one:

but it is more probematic to assign a distance between two photons before they are detected.

I haven't said i need this yet. But if it's a problem, let's clarify this: We are detecting final positions, we know position of the source, so probably (i guess) you are talking about "multipath (many paths) interpretation" of photon. If it's true then:

  1. if you understand (i think this is formal/most common understanding) this interpretation like: photon follows every possible path (with different probability) at the same time, then read my answer i gave to Drakkith (post #28, parts 2 and/or 3)

  2. if you mean photon can follow any path (but one at a time) then it is possible to arrange very simple experiment which should dispel doubts: All we need are 2 satellites orbiting Earth (we need large empty space) and staying in known, constant (and significant - thousand/s of km or so) distance from each other. Then we have to put emitter of photons on one of them and detector on the other (or if you prefere, both devices on the same satellite and mirror on the other). And now all we have to do is to measure precisely time it takes the photon to reach the detector (the longer the distance the better precision. that's why we can't do this experiment in laboratory at short distances - we don't have proper equipment). Knowing the fact (if you disagree go back to point #1) photon is traveling with exact speed of the light we would be able to calculate length of the path. And believe me, this length shoudn't be longer than a couple of cm of the distance between satellites - there are real experiments already showing us this. Taking into account limited precision of measurement equipment, we can conclude it is even the same distance, so: there is only one path photon can follow: STRAIGHT LINE - this is how in real life(not some questionable theories made for special cases) photon behaves.

  3. by the way, even according to those multipath theories, when between points A and B there are NO OBSTACLES, it can be said that path is also straight line or more precisely: straight line is the path with highest probability! Photon (or "parts" of photon - depends on multipath interpretation you use) can in theory follow any other path but probability it does is very low. So we can assume that in majority of cases we know the path. It should be enough to perform all measurements, find regularity - in the worst case we can repeat measurements if needed, calculate avarage, etc. And in my experiment, there is exactly no obstacles - we have source, empty space, and detector (the first material object photon will meet) - only other photons.

So no matter what option you will choose everything should fit (be ok).

What you have written is a very pop-sciencey...
You have been repeatedly asked...

Making such statements without showing where someone is wrong, gently speaking: will not convince anybody. And the only way to point where someone is wrong is to understand him/her first. And the key to understand him/her first is to stop making such unneeded statements - what you have been repeatedly asked.

If you understand what i try to say, why are you asking for a clear problem statement? And if you don't understand, how do you know my interpretation is "pop-sciencey" not knowing what i mean?

Just because I'm not using formal nomenclature (i don't deny) doesn't mean i have wrong imagination about some phenomenons. Better check your own posts and you will see you don't find anything very useful there. They consist mostly of "correcting" almost every single sentence (even inferior ones) I've wrote, what except sounding more "professional", in most cases doesn't change meaning at all. Adding to them some completely unneeded informations (most recent example: "...in proportion to the square of that distance...") - just to show me you know better. Sorry, but you don't convince me this way. By the way: try to strip some modern theories from "professional" terms and then you will really see what "pop-science" is (photon following many paths is one of them).

And at the end:

My sentence: E-M wave is nothing more then electric/magnetic field fluctuations which propagate in space.
Your comment: This is incorrect. Classical EM has everything to do with electric/magnetic field fluctuations which propagate in space

This is from your post #16. Am i using some strange grammar or one mistake ("than" vs "then") changes everything?
 
  • #31
me said:
What you have written is a very pop-sciencey...
You have been repeatedly asked...
I have been telling you where you are going wrong.
Here it is again:
What you have written is a very pop-sciencey way of describing particle physics in relation to classical wave theory. You have been repeatedly told this is not a good way to go forward as it is almost certain that your problem is related to a misunderstanding this approach tends to produce.

You have been repeatedly asked for a clear problem statement, that and you have repeatedly ignored that request. If you do not come up wit a problem statement, we cannot help you.
Please stop beating around the bush.


Please address these issues.
Please avoid pop-science pseudo-arguments.
Please make a clear problem statement.
Please stop beating around the bush.

Good luck.
 
  • #32
Gfgts, I spent a while attempting to respond to your posts, but frankly I got tired of the meandering in your posts, claims that I/we don't know what we're talking about, and your poor attitude in general towards us. I highly advise you to type less rhetoric and be more direct. Have a nice day.
 
  • #33
Drakkith said:
Gfgts, I spent a while attempting to respond to your posts..

I've started this thread and in my original post there were no questions about quantum physics, generally only simple fact that light is quantized somehow. It was mainly YOU who directed entire discussion to what we are talking about right now - first by telling me i can't localise photons in space like i can do with particles, then that it's not possible to know their path. I don't know if you realize but the main motive/theme of the thread is completely lost thanks to this. No one will read thread which is almost about everything. Only people commenting single (out of context) sentences can appear which will cause even more chaos. In other words: YOU (mainly) have caused thet my problem will never be answered (at least in this thread). You could do it but ONLY if you have had very good reasons/arguments. I've waited patiently for them.

The only person the that can feel resentful is ME MYSELF. This is very not fair telling me, after literally "cancelling" my post, you've "spent a while attempting to respond to" my posts, because it took me MUCH MORE time to wrote this. And all this explanation was written just because of YOU. No one else will even read this. It was your free will to choose whether even talk with me. But now, after making some damages, it's your obligation (not favor) to explain why you've done this or at least admit you were wrong - not saying that you are tired/bored.

...claims that I/we don't know what we're talking about...

It's my right to say so, and i don't feel offended if you will do the same (by the way: telling me i need modern some theories is exactly like telling me i don't know what I'm talking about). BUT after telling me i don't know what I'm talking about, you HAVE TO prove it somehow. And here is the difference between me and you. In my last post I've pointed out you are quoting wrong physics laws (any objections?) and I've shown you some paradoxes such theories lead to (it undermines more fundamental physics laws). If this is not an explanation then what is? I'm not just claiming, I'm trying to show weak points and give some examples. The key concept of my last post is: speed of the light - something more fundamental then everything else. I've shown that you have to exceed it, when you want your theories to work - i wouldn't call it "meandering".

...your poor attitude in general towards us...

Excuse me?! Isn't it poor attitude towards me (someone anonymous to you) telling I'm wrong after reading couple of sentences written by some other anonymous? Speaking about "meandering in my posts" and at the same time taking seriously theories in which photon "goes via Alpha Centauri". Such split of personality is especially visible in your case. You are arguing with me but at the SAME TIME being blindly uncritical to comments of almost everyone else - it's hard to find example of worse attitude towards some person. I'm at least critical to some theories not specific persons.

...less rhetoric and be more direct...

I'm as direct as i can be. In short: how E-M radiation at large distance from the source looks like? - i need informations from real experiments (if any) not predictions of some hypothesis. Simple, isn't it? It's not my fault you are using some theories and you don't understand the question. You (all) have created the situation when i can't proceed without, at least partially, refute them. Of course i can't do this in one sentence. Although, reading my explanation took you less time than you lost reading about some modern theories - so don't complain.

Have a nice day.

If you wanted to say you've finished responding to my posts, i can only agree. Further discussion has no sense. why can't you say it directly?
 
  • #34
Simon Bridge said:
I have been telling you where you are going wrong.

The only thing i can really see in your posts is a bunch of insinuations without arguments. I have been telling you that if you want to use statements like: "pop-science", "pseudo-arguments" you have to prove it somehow, otherwise it's nothing more than arrogant insult made most likely due to lack of knowledge, that prevents the formulation of substantial answer. I ALWAYS try to explain my motives when i use such statements, you don't. I'm wondering, why are you doing it? This is public thread, everyone can read what you've written and verify your claims.

The last constructive comment you've made, read: "...more probematic to assign a distance between two photons before they are detected" (post #27). It was the last sentence in the paragraph, you didn't specify what EXACTLY you meant. So, i interpreted it in this way, that you were talking about so called: multipath (many paths) theory of photon. And i told what i think about such theories and also explained why. If you were talking about something else then you got an opportunity to clarify this in your last post. You didn't even mention about it. So my question is simple:

What exactly do you mean saying: "...more probematic to assign a distance between two photons before they are detected"?

Next time be more specific.

My sentence: E-M wave is nothing more then electric/magnetic field fluctuations which propagate in space. Your comment: This is incorrect. Classical EM has everything to do with electric/magnetic field fluctuations which propagate in space. (post #16)

I'm asking again: Am i using some strange grammar or one mistake ("than" vs "then") changes everything? If i made mistake you can help me avoid it in the future. If you not carefully read, correct your comment. Saying i don't know what I'm talking about is one thing but claiming that i said something i never said is a little bit too much. You've gone too far (if you did it intentionally). Clarify this.
 
  • #35
This thread has devolved into the equivalent of name calling. Thread locked.
 
<h2>1. What is the cross-section area of a single electromagnetic (E-M) wave?</h2><p>The cross-section area of a single E-M wave is the area that is perpendicular to the direction of the wave's propagation. It represents the physical extent of the wave in space.</p><h2>2. How does the cross-section area of an E-M wave change with distance?</h2><p>The cross-section area of an E-M wave does not change with distance. It remains constant as the wave propagates through space.</p><h2>3. What factors affect the cross-section area of an E-M wave?</h2><p>The cross-section area of an E-M wave is affected by the wavelength and amplitude of the wave. A shorter wavelength and larger amplitude will result in a smaller cross-section area, while a longer wavelength and smaller amplitude will result in a larger cross-section area.</p><h2>4. Can the cross-section area of an E-M wave be measured?</h2><p>Yes, the cross-section area of an E-M wave can be measured using specialized equipment such as antennas or receivers. These devices can detect and measure the strength of the E-M wave, which can then be used to calculate the cross-section area.</p><h2>5. Is the cross-section area of an E-M wave constant for all types of waves?</h2><p>No, the cross-section area of an E-M wave can vary depending on the type of wave. For example, a plane wave will have a constant cross-section area, while a spherical wave will have a varying cross-section area that decreases with distance from the source.</p>

Related to How cross-section area of single E-M wave looks like?

1. What is the cross-section area of a single electromagnetic (E-M) wave?

The cross-section area of a single E-M wave is the area that is perpendicular to the direction of the wave's propagation. It represents the physical extent of the wave in space.

2. How does the cross-section area of an E-M wave change with distance?

The cross-section area of an E-M wave does not change with distance. It remains constant as the wave propagates through space.

3. What factors affect the cross-section area of an E-M wave?

The cross-section area of an E-M wave is affected by the wavelength and amplitude of the wave. A shorter wavelength and larger amplitude will result in a smaller cross-section area, while a longer wavelength and smaller amplitude will result in a larger cross-section area.

4. Can the cross-section area of an E-M wave be measured?

Yes, the cross-section area of an E-M wave can be measured using specialized equipment such as antennas or receivers. These devices can detect and measure the strength of the E-M wave, which can then be used to calculate the cross-section area.

5. Is the cross-section area of an E-M wave constant for all types of waves?

No, the cross-section area of an E-M wave can vary depending on the type of wave. For example, a plane wave will have a constant cross-section area, while a spherical wave will have a varying cross-section area that decreases with distance from the source.

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