Where does interference occur in light waves?

[Cthugha]

The point is that electromagnetic wave equation describes actual spatial wave where electric and magnetic fields oscillate, that is move "up-down"/"left-right" through actual spatial distance of their amplitudes as they propagate.

NO, the oscillations in an em wave do exactly not mean that. It is a change in the field strength along some direction. The change in field strength does not mean that something is literally moving up or down in this direction. Could you please provide a reference confirming that these are indeed mechanical-like oscillations and not oscillations in the electrical field as Wikipedia and many other sources say?

What do you mean amplitude is "in electric field"?

Exactly that: The electric field strength oscillates, it increases and decreases again and so on and so forth.

That's not my model, it's what Maxwell came up with. Combined electric and magnetic field and it turned out they would oscillate while propagating at the speed of light. Then Einstein figured out they have momentum, making them "full-fledged particles", to quote Wikipedia.

Maxwell did not come up with a model for photons. He came up with a great model for light beams and large numbers of photons. Speaking about single photons (ensembles of identically prepared single photons), you can only recover some analogue to Maxwell's equations in a probabilistic manner and considering many repeated runs of an experiment. However, you still run into conceptual problems. For example, there is a weak uncertainty relation between photon number and phase. As the photon number is precisely determined for a single photon, phase is pretty much undetermined. This is something you do not get out of Maxwell's model.

 

[sophiecentaur]

Not tiny balls, it's oscillating electromagnetic fields, where their oscillation is defined by their wavelength and amplitudes. That's what Maxwell said and found out the speed of propagation of such oscillating electromagnetic fields would be the speed of light. Coincidence?

Our unit for distance, whole General and Special Relativity, and much of the rest of the physics depends on this electromagnetic oscillation propagating in straight lines. That's also necessary for the speed of light be constant. Just because we have no practical explanation to what happens at the double slit doesn't mean have to abandon the idea photons propagate along straight lines.

Then for our experiment we obviously need to place the detector at focus point distance. But it's not really important if we can detect individual photons, so the critical question to answer is if we could make pixels small enough whether a single photon could ever impact more than one pixel.

Maxwell had nothing to do with Quantum Mechanics. His model was a classical one. It seems that you fail to see the difference (which is what this is all about). Your personal argument glides seamlessly between classical and QM and you don't even seem aware that you are doing it.

I notice you are still ignoring my challenge to relate this to Long Wave Radio. If you can't do this then your model has to be a dead duck. Btw, you don't mean "pixel"; you mean 'detector'. The detector on the shelf in your home (your radio receiver) is around 1/3000 of the wavelength of the lowest frequency it will receive perfectly well. How does that fit your idea of a photon, as you have described it, being 'focussed' onto a detector?

Can I ask what level of formal Physics and or Maths education you have? It could make a difference to how you appreciate some of what you have been reading recently.

 

[MarkoniF]

NO, the oscillations in an em wave do exactly not mean that. It is a change in the field strength along some direction. The change in field strength does not mean that something is literally moving up or down in this direction. Could you please provide a reference confirming that these are indeed mechanical-like oscillations and not oscillations in the electrical field as Wikipedia and many other sources say?

It does mean electric and magnetic fields are actually moving, that's what electromagnetic wave equation describes. If they didn't then the plane of B field oscillation couldn't be perpendicular to the plane of E field oscillation, there wouldn't be any "plane", there couldn't be such thing as horizontal, vertical or circular polarization.

http://en.wikipedia.org/wiki/Electromagnetic_wave_equation
- "The electromagnetic wave equation is a second-order partial differential equation that describes the propagation of electromagnetic waves through a medium or in a vacuum. It is a three-dimensional form of the wave equation."

http://en.wikipedia.org/wiki/Electromagnetic_radiation
- "EMR has both electric and magnetic field components, which stand in a fixed ratio of intensity to each other, and which oscillate in phase perpendicular to each other and perpendicular to the direction of energy and wave propagation."

http://en.wikipedia.org/wiki/Electromagnetic_radiation
- "Electromagnetic radiation is a transverse wave, meaning that the oscillations of the waves are perpendicular to the direction of energy transfer and travel."

http://en.wikipedia.org/wiki/Electromagnetic_radiation

- "This diagram shows a plane linearly polarized EMR wave propagating from left to right. The electric field is in a vertical plane and the magnetic field in a horizontal plane."

Exactly that: The electric field strength oscillates, it increases and decreases again and so on and so forth.

That too, but unlike polarization plane, that is spatial oscillation, I don't think magnitude oscillation can be experimentally confirmed.

Maxwell did not come up with a model for photons. He came up with a great model for light beams and large numbers of photons. Speaking about single photons (ensembles of identically prepared single photons), you can only recover some analogue to Maxwell's equations in a probabilistic manner and considering many repeated runs of an experiment. However, you still run into conceptual problems. For example, there is a weak uncertainty relation between photon number and phase. As the photon number is precisely determined for a single photon, phase is pretty much undetermined. This is something you do not get out of Maxwell's model.

Single photons do too have specific polarization and wavelength. Inability to measure something with certainty doesn't mean it's actually undefined or unreal.

 

[MarkoniF]

Maxwell had nothing to do with Quantum Mechanics. His model was a classical one. It seems that you fail to see the difference (which is what this is all about). Your personal argument glides seamlessly between classical and QM and you don't even seem aware that you are doing it.

Does QM in any way discredits photon is oscillation of electric and magnetic fields, with certain wavelength and polarization plane?

I notice you are still ignoring my challenge to relate this to Long Wave Radio. If you can't do this then your model has to be a dead duck.

How does that fit your idea of a photon, as you have described it, being 'focussed' onto a detector?

Do what? It's not MY model, stop flattering me please, you make me blush. It's common knowledge described in electrodynamics textbooks. So anyway, what is it "I" am ignoring, what is your objection about? What do you imagine would be the problem, something to do with focus? What is it?

Btw, you don't mean "pixel"; you mean 'detector'. The detector on the shelf in your home (your radio receiver) is around 1/3000 of the wavelength of the lowest frequency it will receive perfectly well.

I mean pixel, but I can call it "photoreceptor" if you prefer. Photo detectors are made of pixels with certain size, which is what defines detector resolution. These guys call them pixels as well:

http://phys.org/news173957578.html
- "camera capable of filming individual photons one million times a second... a pixel that is 50 microns-by-50 microns... "

Can I ask what level of formal Physics and or Maths education you have? It could make a difference to how you appreciate some of what you have been reading recently.

Let's just say I'm self-proclaimed know-it-all smarty-pants type of person, like you, and everyone else on the internet.

 

[sophiecentaur]

Does QM in any way discredits photon is oscillation of electric and magnetic fields, with certain wavelength and polarization plane?


Do what? It's not MY model, stop flattering me please, you make me blush. It's common knowledge described in electrodynamics textbooks. So anyway, what is it "I" am ignoring, what is your objection about? What do you imagine would be the problem, something to do with focus? What is it?

I mean pixel, but I can call it "photoreceptor" if you prefer. Photo detectors are made of pixels with certain size, which is what defines detector resolution. These guys call them pixels as well:

http://phys.org/news173957578.html
- "camera capable of filming individual photons one million times a second... a pixel that is 50 microns-by-50 microns... "

Let's just say I'm self-proclaimed know-it-all smarty-pants type of person, like you, and everyone else on the internet.

Yes. Completely and utterly. This is my whole point. Whatever you have read is either wrong or you are not reading the whole of what is written - as with your selective choice of the one diagram describing waves in the wiki article about photons. Did you actually read the whole of the caption beneath that diagram, which refers to 'hisorically'? What does the rest tell you?

Again, it is totally the other way round A very (infinitely) small detector has no resolution at all - it is omnidirectional. Basic diffraction theory. You may be referring to the focussing system or the 'wave gathering structure' that presents a receptor with an image with certain resolution. (Look up resolution of a lens or antenna.)

That is making a massive assumption about all the people who post on PF. Many of them are extremely well informed and come here to meet like minded contributors. The average level of BS on PF is well below the norm on the Web.

I see you spent a whole post 'explaining' some of the basic nature of EM waves but rather missing the point about what moves, physically and what doesn't move. Fields do not move. They just have a value at some point in space. A disturbance in a field can propagate in space as a wave in the same way that sound can propagate along a string without any of the string actually going anywhere, only the Electric and Magnetic fields do not themselves, represent a lateral movement of anything.

 

[sophiecentaur]

@MarcoinF
Please address my point about your ideas relative to Long Wave radio signals. It could be very enlightening for you. You seem to shy away from that concern of mine. Why?

 

[MarkoniF]

Yes. Completely and utterly. This is my whole point.

What are you talking about? You forgot to explain yourself. Can you articulate how do you imagine QM invalidates photons are oscillating electric and magnetic fields?

Again, it is totally the other way round A very (infinitely) small detector has no resolution at all - it is omnidirectional. Basic diffraction theory. You may be referring to the focussing system or the 'wave gathering structure' that presents a receptor with an image with certain resolution. (Look up resolution of a lens or antenna.)

I was talking about photo-detectors, such as photographic film, and they do have finite resolution defined by the pixel size. What's the problem?

I see you spent a whole post 'explaining' some of the basic nature of EM waves but rather missing the point about what moves, physically and what doesn't move.

You are missing the point and you are not saying anything but simply negating without any reason or explanation given. If the fields didn't move then the plane of B field oscillation couldn't be perpendicular to the plane of E field oscillation, there wouldn't be any "plane", there couldn't be such thing as horizontal, vertical or circular polarization. How do you arrive to your conclusion to disagree with this?

Fields do not move. They just have a value at some point in space.

http://en.wikipedia.org/wiki/Electromagnetic_wave_equation
- "The electromagnetic wave equation is a second-order partial differential equation that describes the propagation of electromagnetic waves through a medium or in a vacuum. It is a three-dimensional form of the wave equation."

Do you know what is wave equation? Do you know what is transverse wave? Do you know what "perpendicular oscillation" means? If you do, then how do you explain yourself thinking electromagnetic wave equation does not describe E and B fields are actually moving, that is oscillating perpendicularly to the direction of their propagation?

A disturbance in a field can propagate in space as a wave in the same way that sound can propagate along a string without any of the string actually going anywhere...

Are you suggesting light is longitudinal waves? Sound is longitudinal waves, light is transverse waves.

http://en.wikipedia.org/wiki/Electromagnetic_radiation
- "Electromagnetic radiation is a transverse wave, meaning that the oscillations of the waves are perpendicular to the direction of energy transfer and travel."

How do you explain yourself thinking there could be "perpendicular oscillation" without E and B field actually moving perpendicularly to the direction of travel?

...only the Electric and Magnetic fields do not themselves, represent a lateral movement of anything.

How did you come up with that?

http://en.wikipedia.org/wiki/Electromagnetic_radiation

- "The electric field is in a vertical plane and the magnetic field in a horizontal plane."

Do you realize charge magnitude +q and -q is scalar while E and B are vectors describing their lateral displacement? What do you think "vertical plane" and "horizontal plane" would be all about? How would you explain horizontal, vertical or circular polarization if there is no lateral plane of oscillation?

Please address my point about your ideas relative to Long Wave radio signals. It could be very enlightening for you. You seem to shy away from that concern of mine. Why?

I'd be happy too, but you missed to explain what do you imagine would be the problem. So I'm asking you again, what is it you would like me to explain? You seem to shy away from actually pointing any problem. It could be very enlightening for you if you did.

 

[sophiecentaur]

What are you talking about? You forgot to explain yourself. Can you articulate how do you imagine QM invalidates photons are oscillating electric and magnetic fields?

I imagine you have read about the 'duality' issue and that, for more than a hundred years, the two facets of Electromagnetism have been appreciated as being very different and do not apply at the same time.

I was talking about photo-detectors, such as photographic film, and they do have finite resolution defined by the pixel size. What's the problem?

An array of sensors has no resolution at all unless an image is focussed on it. Whilst it is obvious that one photon can only activate one sensor on an array, that is not what is meant by resolution. (Look it up)

You are missing the point and you are not saying anything but simply negating without any reason or explanation given. If the fields didn't move then the plane of B field oscillation couldn't be perpendicular to the plane of E field oscillation, there wouldn't be any "plane", there couldn't be such thing as horizontal, vertical or circular polarization. How do you arrive to your conclusion to disagree with this?

http://en.wikipedia.org/wiki/Electromagnetic_wave_equation
- "The electromagnetic wave equation is a second-order partial differential equation that describes the propagation of electromagnetic waves through a medium or in a vacuum. It is a three-dimensional form of the wave equation."

Do you know what is wave equation? Do you know what is transverse wave? Do you know what "perpendicular oscillation" means? If you do, then how do you explain yourself thinking electromagnetic wave equation does not describe E and B fields are actually moving, that is oscillating perpendicularly to the direction of their propagation?

Yes I know what a wave equation is and I can solve it. An equation that describes Forces (which is what a Field will exert on a charge, for instance) does not involve any movement at all. If there were some 'movement' of anything in the transverse direction of the fields then that would involve Work being done, which would mean Energy Loss. There is no energy loss because there is no movement.

Are you suggesting light is longitudinal waves? Sound is longitudinal waves, light is transverse waves.

http://en.wikipedia.org/wiki/Electromagnetic_radiation
- "Electromagnetic radiation is a transverse wave, meaning that the oscillations of the waves are perpendicular to the direction of energy transfer and travel."

How do you explain yourself thinking there could be "perpendicular oscillation" without E and B field actually moving perpendicularly to the direction of travel?

How did you come up with that?

http://en.wikipedia.org/wiki/Electromagnetic_radiation

- "The electric field is in a vertical plane and the magnetic field in a horizontal plane."

Do you realize charge magnitude +q and -q is scalar while E and B are vectors describing their lateral displacement? What do you think "vertical plane" and "horizontal plane" would be all about? How would you explain horizontal, vertical or circular polarization if there is no lateral plane of oscillation?

I know EM waves are transverse, which is why I compared them with waves on strings - which are also transverse. There is no motion of anything, in either case, in the direction of the propagation of the wave. In the case of mechanical waves, there is lateral movement but without energy loss because the KE and PE add together to give a constant level of energy because they are in phase quadrature . There is nothing of the sort in EM waves because there is no work, no PE and no KE.

I'd be happy too, but you missed to explain what do you imagine would be the problem. So I'm asking you again, what is it you would like me to explain? You seem to shy away from actually pointing any problem. It could be very enlightening for you if you did.

The problem is that, for long waves, according to your naive description of a 'wavelike photon' the photons would need to have a length of several wavelengths, which would put it at, perhaps ten kilometres. How would that be picked up on a detector that is only perhaps 10cm long? In your terms of 'resolution', how many 'pixels' would that cover? Certainly not one photon per pixel.

But we have seen that you didn't understand what the straighforward wiki article was telling you about photons - because you have only quoted what it says about waves. rather than reading a couple of pages from me, why not read that article, paying particular attention to what it says about photons and not waves?
Or this discussion

Or this

http://www.researchgate.net/post/What_is_the_cross_section_size_of_a_photon

 

[Cthugha]

It does mean electric and magnetic fields are actually moving, that's what electromagnetic wave equation describes. If they didn't then the plane of B field oscillation couldn't be perpendicular to the plane of E field oscillation, there wouldn't be any "plane", there couldn't be such thing as horizontal, vertical or circular polarization.

ARGH. Again, do you have any peer reviewed references for that claim? These forums have rules you have agreed to, you know. The only spatial movement involved is in the direction the beam travels. The electric field amplitudes changing do not correspond to anything moving up and down. Increasing and decreasing in magnitude is something very different from moving. By the way, this is exactly what your wikipedia quotes say: The electric and magnetic field components oscillate - not something mechanical. So please: what exactly do you think is moving up and down?

If you have the patience, you can also check this thread: https://www.physicsforums.com/showthread.php?t=510552 which answered pretty much the same question.

That too, but unlike polarization plane, that is spatial oscillation, I don't think magnitude oscillation can be experimentally confirmed.

How about learning the basics before making bold claims?

Single photons do too have specific polarization and wavelength.

Maybe. You can prepare single photons as polychromatic and as polarized or partially polarized as you want to (or your equipment allows).

Inability to measure something with certainty doesn't mean it's actually undefined or unreal.

Uncertainty relations are not about inability to measure something. Please read up on the basics.

 

[MarkoniF]

I imagine you have read about the 'duality' issue and that, for more than a hundred years, the two facets of Electromagnetism have been appreciated as being very different and do not apply at the same time.

Can you actually point anything specific in QM that contradicts my naive, yet beautifully elegant, notion how photons are oscillating electric and magnetic fields?

An array of sensors has no resolution at all unless an image is focussed on it. Whilst it is obvious that one photon can only activate one sensor on an array, that is not what is meant by resolution. (Look it up)

An array of photo-receptors has resolution defined by the size of those light-sensitive pixels, which is the property of that whole detector surface and independent of whether you focus image on it or not. I don't see it is obvious a single photon could not activate more than one pixel, I think that's very interesting question.

Yes I know what a wave equation is and I can solve it. An equation that describes Forces (which is what a Field will exert on a charge, for instance) does not involve any movement at all.

Force? Between what? No. There are no any lines of force when talking about single electric or magnetic fields, only field lines. You would need a separate "test" charge in order to speak of any force, and the vector of the force would be relative to the position of that test charge, nothing that would make E and B perpendicular to each other and perpendicular to the direction of their propagation.

If there were some 'movement' of anything in the transverse direction of the fields then that would involve Work being done, which would mean Energy Loss. There is no energy loss because there is no movement.

If there is no damping, there is no energy loss.

I know EM waves are transverse, which is why I compared them with waves on strings - which are also transverse. There is no motion of anything, in either case, in the direction of the propagation of the wave. In the case of mechanical waves, there is lateral movement but without energy loss because the KE and PE add together to give a constant level of energy because they are in phase quadrature . There is nothing of the sort in EM waves because there is no work, no PE and no KE.

I think it's pretty clear what "perpendicular oscillation" means and I think I provided plenty of references stating exactly that. Here is one more:

http://en.wikipedia.org/wiki/Electromagnetic_radiation
- "From the viewpoint of an electromagnetic wave traveling forward, the electric field might be oscillating up and down, while the magnetic field oscillates right and left..."


I don't know how more plainly that can be said, and if those vectors were not spatial, describing change in position, but some direction of "force" as you say, then surely someone somewhere would have mentioned it. So how about you now provide some reference that explains what is oscillating in electromagnetic wave if it's not E and B fields actually moving laterally to the direction of photon propagation?

The problem is that, for long waves, according to your naive description of a 'wavelike photon' the photons would need to have a length of several wavelengths, which would put it at, perhaps ten kilometres. How would that be picked up on a detector that is only perhaps 10cm long?

There is no any length, wavelength is simply defined by the distance where E and B fields (point field sources) cross paths, or the distance between the two points in space where they reach the peaks of their amplitude. What does length of the detector have to do with the wavelength? It's the amplitude that defines photon "thickness". Small or thin antenna would catch short bullets with about the same probability as it would catch long arrows, given they have the same thickness, so it would be the same for short and long wavelength photons.

In your terms of 'resolution', how many 'pixels' would that cover? Certainly not one photon per pixel.

It would depend on how big is the amplitude and how big pixels are, and also it would depend on how far away are these oscillating fields from the center line at the moment of impact. According to my naively literal and wonderfully marvelous interpretation a single photon could at most impact two pixels, under condition that we could make those pixels be at least half the size of their full amplitudes.

 

[MarkoniF]

ARGH. Again, do you have any peer reviewed references for that claim? These forums have rules you have agreed to, you know. The only spatial movement involved is in the direction the beam travels. The electric field amplitudes changing do not correspond to anything moving up and down. Increasing and decreasing in magnitude is something very different from moving. By the way, this is exactly what your wikipedia quotes say: The electric and magnetic field components oscillate - not something mechanical. So please: what exactly do you think is moving up and down?

If you have the patience, you can also check this thread: https://www.physicsforums.com/showthread.php?t=510552 which answered pretty much the same question.

I gave plenty of links from Wikipedia stating it's E and B fields that oscillate up and down, or left and right, as they say, which I'd says can mean only one thing. If they meant to say the oscillation is only about some change in magnitude or whatever else, then they would have said so, I believe. But in any case surely someone would, so how about you provide some peer reviewed references that make it clear it's only decreasing/increasing magnitude and not any spatial motion involved when talking about E and B fields perpendicular oscillation?

How about learning the basics before making bold claims?

Magnitude is a scalar number. Change in magnitude can not define any planes or directions of oscillation. How about learning some basics before making funny claims?

Uncertainty relations are not about inability to measure something.

You wouldn't know the difference between actual uncertainty or inability to measure something with certainty as long as you can't actually measure it with certainty.

 

[Cthugha]

I gave plenty of links from Wikipedia stating it's E and B fields that oscillate up and down, or left and right, as they say, which I'd says can mean only one thing.

Yes, this means that there is a good reason Wikipedia is not a respected peer-reviewed source. It really is not. I corrected so many mistakes there myself which just keep reappearing, that it is extremely frustrating.

If they meant to say the oscillation is only about some change in magnitude or whatever else, then they would have said so, I believe. But in any case surely someone would, so how about you provide some peer reviewed references that make it clear it's only decreasing/increasing magnitude and not any spatial motion involved when talking about E and B fields perpendicular oscillation?

See the thread I linked to before or this thread (https://www.physicsforums.com/showpost.php?p=3986399&postcount=70) or read up on it in the Mandel/Wolf (optical coherence and Quantum Optics - especially chapter 12.11 may be of interest to you). However, I do not know your background, but I assume the math in there is too complex. The book on optics by Hecht may work on your level, maybe the Jackson works. In principle ANY textbook which introduces the em field may work as it explains what it means: Each vector represents the value (magnitude and direction) of the electric (blue) or magnetic (field) at the point where the tail of the vector lies (this is of course not a valid reference, but as I took the wording from another page, I should mention it here: http://physics.stackexchange.com/questions/20331/understanding-the-diagrams-of-electromagnetic-waves. There, exactly the picture you posted is discussed. The important thing is the "at the point where the tail of the vector lies".

As another handwaving explanation: If there actually was something moving up and down, the distance traveled would increase with the amplitude of the oscillation. That, however, would mean that the motion perpendicular to the direction of the oscillation must get slower as the speed of light is a constant. It is well accepted that the speed of light does not depend on the intensity of the light in question in this manner.

Magnitude is a scalar number. Change in magnitude can not define any planes or directions of oscillation. How about learning some basics before making funny claims?

Ehm...you are aware that vectors have a magnitude, too, no?

You wouldn't know the difference between actual uncertainty or inability to measure something with certainty as long as you can't actually measure it with certainty.

That is pseudoscientific gibberish. The uncertainty principle is VERY well understood.

 

[sophiecentaur]

Can you actually point anything specific in QM that contradicts my naive, yet beautifully elegant, notion how photons are oscillating electric and magnetic fields?

Do you not think that, if the picture you have in your mind were the really near the truth, someone (many people) before you would not have published it and we could all go home happy? Could you not just consider that you may have over-simplified it all and that it may just be a tad more difficult than that?

An array of photo-receptors has resolution defined by the size of those light-sensitive pixels, which is the property of that whole detector surface and independent of whether you focus image on it or not. I don't see it is obvious a single photon could not activate more than one pixel, I think that's very interesting question.

If you read anything about QM and how photons interact with systems, you might understand how optical photons interact with just one electron in a detector.

Force? Between what? No. There are no any lines of force when talking about single electric or magnetic fields, only field lines. You would need a separate "test" charge in order to speak of any force, and the vector of the force would be relative to the position of that test charge, nothing that would make E and B perpendicular to each other and perpendicular to the direction of their propagation.

It might be a good idea for you to look up the term 'Field' to find out how it is defined.

If there is no damping, there is no energy loss. I

I think it's pretty clear what "perpendicular oscillation" means and I think I provided plenty of references stating exactly that. Here is one more:

http://en.wikipedia.org/wiki/Electromagnetic_radiation
- "From the viewpoint of an electromagnetic wave traveling forward, the electric field might be oscillating up and down, while the magnetic field oscillates right and left..."


I don't know how more plainly that can be said, and if those vectors were not spatial, describing change in position, but some direction of "force" as you say, then surely someone somewhere would have mentioned it. So how about you now provide some reference that explains what is oscillating in electromagnetic wave if it's not E and B fields actually moving laterally to the direction of photon propagation?

In the definition of a field (read it) there is no mention of any motion. More or less everyone, everywhere' explains that when the term 'Field' is explained.

There is no any length, wavelength is simply defined by the distance where E and B fields (point field sources) cross paths, or the distance between the two points in space where they reach the peaks of their amplitude. What does length of the detector have to do with the wavelength? It's the amplitude that defines photon "thickness". Small or thin antenna would catch short bullets with about the same probability as it would catch long arrows, given they have the same thickness, so it would be the same for short and long wavelength photons.
It would depend on how big is the amplitude and how big pixels are, and also it would depend on how far away are these oscillating fields from the center line at the moment of impact. According to my naively literal and wonderfully marvelous interpretation a single photon could at most impact two pixels, under condition that we could make those pixels be at least half the size of their full amplitudes.

I gave plenty of links from Wikipedia stating it's E and B fields that oscillate up and down, or left and right, as they say, which I'd says can mean only one thing. If they meant to say the oscillation is only about some change in magnitude or whatever else, then they would have said so, I believe. But in any case surely someone would, so how about you provide some peer reviewed references that make it clear it's only decreasing/increasing magnitude and not any spatial motion involved when talking about E and B fields perpendicular oscillation?

Magnitude is a scalar number. Change in magnitude can not define any planes or directions of oscillation. How about learning some basics before making funny claims?

You wouldn't know the difference between actual uncertainty or inability to measure something with certainty as long as you can't actually measure it with certainty.

All this implies that you haven't read what Heisenberg says, that you haven't read how Fields or vectors are defined and that you seem to think that reiterating some Secondary School definitions about waves proves anything about the nature of photons.
I just wonder what you see when you read what a basic textbook has to say about the E and H fields in an EM wave. Do you miss out every other word / line / paragraph or do you just insert extra mis-leading stuff?
I can see you are convinced you are right about this. Has anyone joined in this thread to support your unlikely ideas? (Or are we all just plain ignorant?)

 

[Cthugha]

I don't see it is obvious a single photon could not activate more than one pixel, I think that's very interesting question.

Oh, I only saw that point right now. Well, it may indeed not have been obvious up to the 1950s, but since then this question is solved. This is called antibunching and is THE experimental test to check whether you indeed have prepared a single photon state. The experiment goes as follows: shine your light field on a beam splitter, place one spad (single photon avalanche diode) at each output port and perform coincidence counting to find out how often these two diodes show detections at the same time. For single photons these never fire simultaneously, for coherent or thermal light of the same mean intensity they do.

 

[sophiecentaur]

Oh, I only saw that point right now. Well, it may indeed not have been obvious up to the 1950s, but since then this question is solved. This is called antibunching and is THE experimental test to check whether you indeed have prepared a single photon state. The experiment goes as follows: shine your light field on a beam splitter, place one spad (single photon avalanche diode) at each output port and perform coincidence counting to find out how often these two diodes show detections at the same time. For single photons these never fire simultaneously, for coherent or thermal light of the same mean intensity they do.

Does that mean that the total number of counts is higher for thermal light in that experiment? Or that, during a random set of counts, some happen to coincide? There are Energy implications here, I think.

 

[MarkoniF]

Yes, this means that there is a good reason Wikipedia is not a respected peer-reviewed source. It really is not.

Wikipedia has citations and references. Articles are put together from what is written in peer-reviewed papers and textbooks, which makes it pretty good source. It's also peer-reviewed itself, in a way, but in any case is certainly far better than links to what some random people said in some forum discussion.

See the thread I linked to before or this thread (https://www.physicsforums.com/showpost.php?p=3986399&postcount=70) or read up on it in the Mandel/Wolf (optical coherence and Quantum Optics - especially chapter 12.11 may be of interest to you). However, I do not know your background, but I assume the math in there is too complex. The book on optics by Hecht may work on your level, maybe the Jackson works.

Links to forum discussions are not proper reference. You read up on Mandel/Wolf and realize you are mistaken. If your understanding of equations was any good you should realize electromagnetic wave equation is actual WAVE EQUATION, describing three-dimensional transverse wave. Oscillating magnitude by itself can not produce anything like that.

In principle ANY textbook which introduces the em field may work as it explains what it means: Each vector represents the value (magnitude and direction) of the electric (blue) or magnetic (field) at the point where the tail of the vector lies (this is of course not a valid reference, but as I took the wording from another page, I should mention it here: http://physics.stackexchange.com/questions/20331/understanding-the-diagrams-of-electromagnetic-waves. There, exactly the picture you posted is discussed. The important thing is the "at the point where the tail of the vector lies".

No. Any textbook will tell you the same thing what I showed you from several Wikipedia articles. You fail to understand "oscillating magnitude" has no any direction, it can not produce any vectors. And the fact you are referencing some forum discussions and random character David Zaslavsky, fourth year graduate student, is not even funny any more, especially since none of that in no way confirms your mistaken assumptions.

As another handwaving explanation: If there actually was something moving up and down, the distance traveled would increase with the amplitude of the oscillation. That, however, would mean that the motion perpendicular to the direction of the oscillation must get slower as the speed of light is a constant. It is well accepted that the speed of light does not depend on the intensity of the light in question in this manner.

No, travel path of a wave is defined by its propagation direction, not path of oscillations.

Ehm...you are aware that vectors have a magnitude, too, no?

Magnitude is not a vector, it's a scalar number. Change in magnitude can not define any direction or plane of oscillation.

 

[sophiecentaur]

Magnitude is not a vector, it's a scalar number. Change in magnitude can not define any direction or plane of oscillation.

You don't seem to realize that we all know stuff like that. You really are trying to teach your Grandmothers to suck eggs. Read a bit about Vectors. Find out about what is meant by a Vector Quantity. Do Vectors not have a Magnitude? Do all Vectors represent Displacement? I don't even know what it is you're trying to hang onto any more. I just think you don't want to be wrong, whatever the facts happen to be. Did anyone actually ever tell you this rubbish?

If the speed of light cannot be exceeded then how can it take a roundabout route along a wiggly path and yet have a speed of c along its line of propagation, which is what you are implying?

 

[Cthugha]

Oh, I just noticed that you are the same guy who repeatedly claimed that one can generate a constant current in an isolated wire in this thread:
https://www.physicsforums.com/showthread.php?t=658810
and were completely resistant to any corrections and also made wrong claims there despite being corrected several times. I thought you were really here to learn something. If I had known beforehand that trolling is your sole intention, I would not even have replied to you.

Wikipedia has citations and references. Articles are put together from what is written in peer-reviewed papers and textbooks, which makes it pretty good source. It's also peer-reviewed itself, in a way, but in any case is certainly far better than links to what some random people said in some forum discussion.

The rules of these forums explicitly exclude Wikipedia as a reliable peer-reviewed source and there are good reasons for that. You agreed to these rules, so I do not think there is any point for discussion here. By the way the exact statement you quoted is not backed up by any reference in the wiki article and it is explicitly presented as a simplified visualization by an "might be".

Links to forum discussions are not proper reference. You read up on Mandel/Wolf and realize you are mistaken. If your understanding of equations was any good you should realize electromagnetic wave equation is actual WAVE EQUATION, describing three-dimensional transverse wave. Oscillating magnitude by itself can not produce anything like that.

Well, certainly better than wikipedia, but I already assumed that you would not read them and the references inside. If you can tell me your background and level of math I can come up with, I can give you more references. But I suppose it is not much use to come up with books like Schleich's quantum optics in phase space if you do not have the proper background to understand it. And again, I think, you are misunderstanding on purpose. I said that you have an oscillating field strength in transversal directions to the beam propagation, while actual movement takes places in the direction of beam propagation. This is school stuff and it is simple. A vector has some position it is associated with and three values giving its three components in a cartesian coordinate system. If you have a look at the three values at some position at some time and notice that these three values are the same at a later time at a close position, this can be considered motion. This is what happens for light in the direction of beam propagation. If you look at a fixed point and notice that the three components change, this is a change of the field. This is NOT motion. It really is that simple. And again: a 3-d wave equation does not say that there is motion in the perpendicular directions. It really is as simple as that.

And I know the Mandel/Wolf quite well, thanks. Do you? It was very helpful in writing my PhD thesis on light fields.^^

No. Any textbook will tell you the same thing what I showed you from several Wikipedia articles. You fail to understand "oscillating magnitude" has no any direction, it can not produce any vectors. And the fact you are referencing some forum discussions and random character David Zaslavsky, fourth year graduate student, is not even funny any more, especially since none of that in no way confirms your mistaken assumptions.

Eh? Oscillating magnitude does not produce vectors? What is that supposed to mean? It is the components of the vectors which oscillate. YOur post makes absolutely no sense. I was just trying to come up with something at your level, which you can actually access. As this is not even university level, but rather school stuff.

No, travel path of a wave is defined by its propagation direction, not path of oscillations.

Finally! So you agree that this is not motion?

Magnitude is not a vector, it's a scalar number. Change in magnitude can not define any direction or plane of oscillation.

Again you are making up things I never said. The electric field changes. This is what I said. For a polarized light field, you can find a transformation, so that only one component of the field is non-zero. This gives you your direction.

 

[MarkoniF]

Do you not think that, if the picture you have in your mind were the really near the truth, someone (many people) before you would not have published it and we could all go home happy? Could you not just consider that you may have over-simplified it all and that it may just be a tad more difficult than that?

This is third time you fail to say anything and instead of answering the question you end up asking me questions. I ask you for the forth time now, can you actually point anything specific in QM that contradicts photons are oscillating electric and magnetic fields?

It might be a good idea for you to look up the term 'Field' to find out how it is defined.

It might be a good idea for you to look up what is 'force' and realize what you originally said is wrong, as I explained.

In the definition of a field (read it) there is no mention of any motion. More or less everyone, everywhere' explains that when the term 'Field' is explained.

We are talking about electromagnetic wave equation (read it), where electric field oscillates in a plane perpendicular to the plane of magnetic field oscillation. You read what is field and realize it's not described by a single vector, it does not describe any plane, and it can not be perpendicular to anything by itself, unless of course it's oscillating within a plane.

All this implies that you haven't read what Heisenberg says, that you haven't read how Fields or vectors are defined and that you seem to think that reiterating some Secondary School definitions about waves proves anything about the nature of photons.

Originally you said it's some force vector that defines plane of E and B field oscillation in electromagnetic wave equation. You were wrong and not surprisingly you failed to provide any reference to support your mistaken assumptions.

I just wonder what you see when you read what a basic textbook has to say about the E and H fields in an EM wave. Do you miss out every other word / line / paragraph or do you just insert extra mis-leading stuff?

http://en.wikipedia.org/wiki/Electromagnetic_radiation
- "Electromagnetic radiation is a transverse wave, meaning that the oscillations of the waves are perpendicular to the direction of energy transfer and travel."

http://en.wikipedia.org/wiki/Electromagnetic_radiation

- "The electric field is in a vertical plane and the magnetic field in a horizontal plane."

http://en.wikipedia.org/wiki/Electromagnetic_radiation
- "From the viewpoint of an electromagnetic wave traveling forward, the electric field might be oscillating up and down, while the magnetic field oscillates right and left..."


Do you see any mention of anything that would suggest those planes of oscillation are defined by some force vectors? Can you provide any other reference that says those planes are not defined by spatial oscillation of E and B field, but some "force vectors" or whatever else?

 

[MarkoniF]

You don't seem to realize that we all know stuff like that. You really are trying to teach your Grandmothers to suck eggs. Read a bit about Vectors. Find out about what is meant by a Vector Quantity. Do Vectors not have a Magnitude? Do all Vectors represent Displacement? I don't even know what it is you're trying to hang onto any more. I just think you don't want to be wrong, whatever the facts happen to be. Did anyone actually ever tell you this rubbish?

Cthugha said planes of E and B fields oscillations are defined by the change of their magnitude. And I said "oscillating magnitude" has no any direction and it can not produce any vectors or planes.

 

[Cthugha]

Does that mean that the total number of counts is higher for thermal light in that experiment? Or that, during a random set of counts, some happen to coincide? There are Energy implications here, I think.

No, such experiments basically measure the variance of the photon number distribution or how "noisy" the photon number distribution is. This may be different for different light fields, even if the mean count rate is the same.

Do you see any mention of anything that would suggest those planes of oscillation are defined by some force vectors?

The strength or magnitude of the electric field at a given point is defined as the force that would be exerted on a positive test charge of 1 coulomb placed at that point.

This is the definition of the electric field. You can read it up in Jackson's book, any other book on electrostatics or dynamics and even in the wikipedia article on the electric field.

Cthugha said planes of E and B fields oscillations are defined by the change of their magnitude. And I said "oscillating magnitude" has no any direction and it can not produce any vectors or planes.

Again you are misinterpreting what I wrote on purpose and twist my words around.

 

[MarkoniF]

Oh, I just noticed that you are the same guy who repeatedly claimed that one can generate a constant current in an isolated wire in this thread:
https://www.physicsforums.com/showthread.php?t=658810
and were completely resistant to any corrections and also made wrong claims there despite being corrected several times. I thought you were really here to learn something. If I had known beforehand that trolling is your sole intention, I would not even have replied to you.

No, I said electric current can be induced in a straight wire, meaning you don't need any loops. Read the links I posted there and learn about it if you don't know. It's only one guy in that thread that doesn't get it, and two other people confirmed what I said. You have no clue, but I like your attempts to discredit me, it's funny.

Eh? Oscillating magnitude does not produce vectors? What is that supposed to mean?

It means oscillating magnitude has no any direction. It also means we should not be surprised you can not provide any reference to support your mistaken opinion.

 

[sophiecentaur]

No, such experiments basically measure the variance of the photon number distribution or how "noisy" the photon number distribution is. This may be different for different light fields, even if the mean count rate is the same.

So you are saying (confirming) that photons have only ever been seen coming out of one slit?


As for MarkoniF, I think it's a hopeless case. I hadn't spotted the name but I should have spotted the 'attitude with no discipline'- as in that last silly thread about wires.

 

[MarkoniF]

The strength or magnitude of the electric field at a given point is defined as the force that would be exerted on a positive test charge of 1 coulomb placed at that point.

This is the definition of the electric field. You can read it up in Jackson's book, any other book on electrostatics or dynamics and even in the wikipedia article on the electric field.

There are no any test charges in electromagnetic wave equation and they would surely not make E and B field oscillate perpendicularly to the direction of wave propagation and to each other.

Again you are misinterpreting what I wrote on purpose and twist my words around.

You wish. This is what you said, and I quote: -"NO, the oscillations in an em wave do exactly not mean that. It is a change in the field strength along some direction. The change in field strength does not mean that something is literally moving up or down in this direction."

I'm telling you again, change in field strength has no any direction and it can not produce any vectors or planes.

 

[MarkoniF]

So you are saying (confirming) that photons have only ever been seen coming out of one slit?


As for MarkoniF, I think it's a hopeless case. I hadn't spotted the name but I should have spotted the 'attitude with no discipline'- as in that last silly thread about wires.

You are hopelessly failing to support your mistaken opinion. I ask you again, can you provide any reference that says those planes are not defined by spatial oscillation of E and B field, but some "force vectors" or whatever else?

 

[sophiecentaur]

I'm telling you again, change in field strength has no any direction and it can not produce any vectors or planes.

Get a grip. What's that supposed to mean?
Fields are in a particular direction - they are Vector quantities, for plane polarised waves, the fields lie in planes and change magnitude and sign. Nothing 'moves' anywhere. But what has any of this basic stuff about waves got to do with the nature of a photon? A photon has no 'size' and could be anywhere. Have you not read that?

 

[Cthugha]

My last comments:

No, I said electric current can be induced in a straight wire, meaning you don't need any loops. Read the links I posted there and learn about it if you don't know. It's only one guy in that thread that doesn't get it, and two other people confirmed what I said. You have no clue, but I like your attempts to discredit me, it's funny.

Two other people confirmed, that you can induce constant currents when having a loop. Without a loop, you induce a current for a short time, electrons pile up at one end of the wire and at some point the induced current and the current that is caused by the repulsion of the large number of electrons piled up cancel, so that there is no net current left. With a loop, there obviously is no pile up and you can induce constant current. But that has already been explained to you in that thread, but you preferred posting you strange view of things.

There are no any test charges in electromagnetic wave equation and they would surely not make E and B field oscillate perpendicularly to the direction of wave propagation and to each other.

The E field is defined via that force and now basically you want to tell us that the definition of some quantity does not matter?

You wish. This is what you said, and I quote: -"NO, the oscillations in an em wave do exactly not mean that. It is a change in the field strength along some direction. The change in field strength does not mean that something is literally moving up or down in this direction."

I'm telling you again, change in field strength has no any direction and it can not produce any vectors or planes.

So you are basically trying to tell me that the "change in the field strength along some direction" (what I have written) does not have any direction? The E-field is not a vector? This is pointless and you do not seem to be interested in physics, but just trolling. I think at this point, it is hopeless to try to get this topic carry some information along for others who might be interested in this topic, so the discussion with you ends here for me. I apologize to the one who opened the thread for being partially responsible that this thread which started out interesting has derailed.

 

[MarkoniF]

Get a grip. What's that supposed to mean?

Get a clue. It means magnitude is a scalar number, thus has no any direction, so therefore change in field strength can not describe any plane and can not be perpendicular to anything.

Fields are in a particular direction - they are Vector quantities, for plane polarised waves, the fields lie in planes and change magnitude and sign.

No, fields can not be described by a single vector. They are not vector quantiites, they are three-dimensional 'vector fields'. A field can not be in a plane. Changing magnitude and sign of a field does not have any direction.

Nothing 'moves' anywhere. But what has any of this basic stuff about waves got to do with the nature of a photon? A photon has no 'size' and could be anywhere. Have you not read that?

http://en.wikipedia.org/wiki/Electromagnetic_radiation

- "The electric field is in a vertical plane and the magnetic field in a horizontal plane."

I ask you again, can you provide any reference that says those planes are not defined by spatial oscillation of E and B field, but some "force vectors" or whatever else?

 

[sophiecentaur]

You are hopelessly failing to support your mistaken opinion. I ask you again, can you provide any reference that says those planes are not defined by spatial oscillation of E and B field, but some "force vectors" or whatever else?

I shouldn't need to be doing that. To be honest, I can't find, anywhere, any statement that insists that a vector quantity has to involve movement or spatial displacement - can you? Searching for a statement that something 'not true' is, indeed 'not true' is a bit of a tall order. If you want to find what 'is true' then take your pic of any google link about what vectors are. You seem to have a problem with defining a Field in terms of its effect on a unit charge (or a unit mass, in the case of gravitational field). Again, that's how they're defined everywhere you care to look. One thing is certain - a Field is not a set of invisible arrows out there in space.
But I think you have got yourself in a hole and you're not actually sure what you are arguing about - and nor am I. Your basic idea is flawed and you haven't come up with any evidence that it isn't.
Why not try to learn something instead of arguing against nothing specific?

 

[MarkoniF]

Two other people confirmed, that you can induce constant currents when having a loop. Without a loop, you induce a current for a short time, electrons pile up at one end of the wire and at some point the induced current and the current that is caused by the repulsion of the large number of electrons piled up cancel, so that there is no net current left. With a loop, there obviously is no pile up and you can induce constant current. But that has already been explained to you in that thread, but you preferred posting you strange view of things.

The argument has nothing to do with "constant" current. It's about whether you need a loop to induce current or can it be done with a straight wire.

The E field is defined via that force and now basically you want to tell us that the definition of some quantity does not matter?

No, I said change in magnitude is not what defines planes of E and B field oscillation.

So you are basically trying to tell me that the "change in the field strength along some direction" (what I have written) does not have any direction?

What direction? What defines that direction and the planes of oscillation? I'm telling you while magnitude does change that is not what defines those planes of oscillation, but it is change of position, i.e. lateral movement of those fields that defines those planes of oscillation. Can you provide any reference that says those planes are not defined by spatial oscillation of E and B field, but something else?

 

[MarkoniF]

I shouldn't need to be doing that. To be honest, I can't find, anywhere, any statement that insists that a vector quantity has to involve movement or spatial displacement - can you? Searching for a statement that something 'not true' is, indeed 'not true' is a bit of a tall order. If you want to find what 'is true' then take your pic of any google link about what vectors are. You seem to have a problem with defining a Field in terms of its effect on a unit charge (or a unit mass, in the case of gravitational field). Again, that's how they're defined everywhere you care to look. One thing is certain - a Field is not a set of invisible arrows out there in space.
But I think you have got yourself in a hole and you're not actually sure what you are arguing about - and nor am I. Your basic idea is flawed and you haven't come up with any evidence that it isn't.

http://en.wikipedia.org/wiki/Electromagnetic_radiation
- "From the viewpoint of an electromagnetic wave traveling forward, the electric field might be oscillating up and down, while the magnetic field oscillates right and left..."

What part of oscillating "up and down" or "left and right" is not clear to you? What else could be oscillating but their lateral position? And if it is something else why was it not mentioned?

You don't need to find a statement that is not true, you only need to find a statement that says what is true, and if that is not spatial oscillation then that statement would say what actually is, like "force vectors" as you said, or whatever else. Can you?

Why not try to learn something instead of arguing against nothing specific?

It is very specific, you just refuse to accept it, because you have fallen in love with complications and mysteries of Quantum Mechanics.

 

[sophiecentaur]

Until you realize that Vectors do not imply movement, there is no point trying to argue with you. Try to take on board some basics before you get assertive. PF is about Physics and not about a special MarkoniF's version.


PS please try to stick to one subject at a time. If you want to start arguing about induced currents could you start another thread or resurrect the old (ranting) one?

 

[MarkoniF]

Until you realize that Vectors do not imply movement, there is no point trying to argue with you. Try to take on board some basics before you get assertive. PF is about Physics and not about a special MarkoniF's version.

I'm not saying vectors generally imply movement, just that in this particular case where we are talking about electromagnetic wave equation "oscillation" of E and B fields indeed refers to their lateral movement.

It is not my version any more than what you say is your special version. I say oscillation vectors are motion vectors and you say it's some force vectors. All I'm asking you now is not to argue but simply point some reference that confirms your version.

 

[Nugatory]

I'm not saying vectors generally imply movement, just that in this particular case where we are talking about electromagnetic wave equation "oscillation" of E and B fields indeed refers to their lateral movement.

No, there's no lateral movement in this oscillation, just cyclical changes in the strength and direction of the fields.

 

[MarkoniF]

No, there's no lateral movement in this oscillation, just cyclical changes in the strength and direction of the fields.

Direction of the fields? What does that mean? Direction of what exactly?

http://en.wikipedia.org/wiki/Electromagnetic_radiation

- "The electric field is in a vertical plane and the magnetic field in a horizontal plane."

What is it that moves up/down and left/right describing horizontal and vertical planes of E and B fields oscillation if not those fields themselves? And how did you come up with your conclusion, what are you referring to?

 

[Drakkith]

Here's my understanding of it.

Take a charged particle and put it in space. Emit an EM wave that will pass over that particle. The electric field will cause the particle to accelerate in a certain direction. The is described by a vector that has a direction AND a magnitude. This vector changes in magnitude over time at the same rate as the frequency of the wave. Once the magnitude of this field rises and falls to zero, it then switches directions and rises and falls again. When it switches the particle is accelerated in the opposite direction as before. The magnitude only describes the strength of the field.

The field itself is not moving. It isn't a physical object and motion can't describe it. What is happening is that the electric and magnetic aspects of the field are changing from one direction to the other in a cyclic fashion. Since a vector is used to describe the EM field, we say the vector is oscillating.

Markonif the picture you linked is NOT a representation of the EM wavefront as it travels. It is only a representation of the field vectors.

Now, I'm no expert, so if that isn't correct then someone please tell me.

 

[MarkoniF]

Here's my understanding of it.

Take a charged particle and put it in space. Emit an EM wave that will pass over that particle. The electric field will cause the particle to accelerate in a certain direction. The is described by a vector that has a direction AND a magnitude. This vector changes in magnitude over time at the same rate as the frequency of the wave. Once the magnitude of this field rises and falls to zero, it then switches directions and rises and falls again. When it switches the particle is accelerated in the opposite direction as before. The magnitude only describes the strength of the field.

What you are describing is force vector relative to some test charge(s). That can not be since electromagnetic wave equation is derived as propagation E and B fields in vacuum. And even if there were some test charges around the path of the photon that would not make planes of E and B field oscillation perpendicular to the direction of propagation and to each other, it would not make it oscillate all the way along the path. There is nowhere nothing even similar to any of what you describe mentioned in any Wikipedia article, or anywhere else. So how did you come up with all that?

The field itself is not moving. It isn't a physical object and motion can't describe it.

Why so adamant about it, why so sure? Can you quote some reference that even alludes it's not the fields themselves that actually move? What makes you think fields are not physical objects? What else can they be, a dream? Fields can have momentum which makes them quite real, very material and physical things.

What is happening is that the electric and magnetic aspects of the field are changing from one direction to the other in a cyclic fashion. Since a vector is used to describe the EM field, we say the vector is oscillating.

What "aspect" of the field changes direction? Single vector can not describe a field, only force between two fields can be expressed by a vector. Fields are geometrical three-dimensional volumes with potentials, and you only get a vector when you pick one particular point in that field relative to its center of origin.

Look at all the articles in Wikipedia about em waves, or wherever else you want, and see how it's everywhere plainly said it's E and B fields that oscillate. How can you interpret that in any other way but as referring to their motion? How can you assume it's something else when nothing else is mentioned?

Markonif the picture you linked is NOT a representation of the EM wavefront as it travels. It is only a representation of the field vectors.

It is representation of electromagnetic wave equation that describes three-dimensional transverse wave. When you plot that equation you are actually piloting POSITION of E and B fields, not their magnitude or whatever force vectors relative to some test charges, but their position.

http://en.wikipedia.org/wiki/Electromagnetic_wave_equation

 

[berkeman]

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