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Ponderer

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http://www.schoolphysics.co.uk/age1...ons/text/Energy_levels_in_hydrogen/index.html

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In summary, the conversation discusses the concept of photon emission by electrons in an atom, particularly in the case of a hydrogen atom. The website linked provides basic information on calculating the energy and wavelength of a photon emitted by an electron in a hydrogen atom. The conversation also touches on the possibility of having more than one photon emitted at a lower energy, which is deemed unlikely due to the quantization of photons. The concept of 1.2 photons is questioned and it is explained that this cannot occur in our current theories. The exception to this is the phenomenon of spontaneous parametric down conversion (SPDC), which can result in two entangled photons being emitted. The conversation also briefly discusses the limitations of our understanding of photons and the use of quantum

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Ponderer

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http://www.schoolphysics.co.uk/age1...ons/text/Energy_levels_in_hydrogen/index.html

Physics news on Phys.org

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BiGyElLoWhAt

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Just out of curiosity, how would you interpret 1.2 photons? What would .2 photons mean?

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Ponderer

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BiGyElLoWhAt said:What would .2 photons mean?

It would mean h*f*0.2

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Ponderer

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SPDC is the only exception?BiGyElLoWhAt said:Google spontaneous parametric down conversion.

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Physicist97

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BiGyElLoWhAt

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We don't really have a good idea of what a photon is, so to actually give physical meaning to a fraction of a photon (outside of an average) would be really hard to do.

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BiGyElLoWhAt

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Not the only, but it is one example, of which there are many reliable sources to read.Ponderer said:SPDC is the only exception?

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Ponderer

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What about thermal energy from say a hot glowing piece of iron? IOW, would an electron in the hot iron that emits two or more simultaneous photons be a rare event?BiGyElLoWhAt said:Not the only, but it is one example, of which there are many reliable sources to read.

- #9

BiGyElLoWhAt

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Ponderer said:What about thermal energy from say a hot glowing piece of iron? IOW, would an electron in the hot iron that emits two or more simultaneous photons be a rare event?

I would venture to say so. What's different about this case, is that the energy is stored in kinetic energy of the atom, versus with SPDC, it's stored in potential energy of the electron jumping to an outer shell. When the electron jumps out a layer (from say s to d [I think that's the right order, my chem sucks]) it isn't stable, so it collapses back to the previous layer, emitting energy. If the crystal is oriented properly (i.e. non linear) it can emit 2 photons which are entangled. My college uses BBO for this.

As far as why kinetic energy doesn't seem to release 2 photons when it's emitted, I'm not sure, honestly.

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bhobba

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BiGyElLoWhAt said:Just out of curiosity, how would you interpret 1.2 photons? What would .2 photons mean?

They never occur in our theories.

Thanks

Bill

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- #11

bhobba

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BiGyElLoWhAt said:We don't really have a good idea of what a photon is,

And exactly in what way is QED lacking in giving us a 'good idea'?

QED is the most accurately verified physical theory of all time.

Thanks

Bill

- #12

bhobba

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BiGyElLoWhAt said:When the electron jumps out a layer (from say s to d [I think that's the right order, my chem sucks]) it isn't stable, so it collapses back to the previous layer, emitting energy.

I an not sure 'jump' is the best language to use here - transition is probably better. What's going on really requires QED:

https://en.wikipedia.org/wiki/Spontaneous_emission

Thanks

Bill

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Ponderer

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bhobba said:And exactly in what way is QED lacking in giving us a 'good idea'?

But if one formulates equations to predict how a ball bounces, does that explain what's inside the ball or what any possible fields around the ball are made of?

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Ponderer

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What about the NIST experiment?bhobba said:QED is the most accurately verified physical theory of all time.

"The most energetic photons from electron transitions in helium have energies of around 39 electron volts.The photon energy scales as

http://www.npl.washington.edu/AV/altvw167.html

http://www.nist.gov/pml/div684/ebit-112712.cfm

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BiGyElLoWhAt

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@ bhobba how does QED define a photon? Just out of curiosity. Specificly, please.

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bhobba

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Ponderer said:But if one formulates equations to predict how a ball bounces, does that explain what's inside the ball or what any possible fields around the ball are made of?

I think you need to cognate on what explain means.

Our theories depend on assumptions that explain the predictions of the theory.

In your example classical mechanics explains how the ball bounces and doesn't require the other stuff you mentioned.

QED explains the behaviour of photons.

Thanks

Bill

- #17

bhobba

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BiGyElLoWhAt said:@ bhobba how does QED define a photon? Just out of curiosity. Specificly, please.

The quantum of the quantised EM field.

Further detail requires studying the theory, but loosely its analogous to the creation and annihilation operators of the quantum harmonic oscillator:

https://en.wikipedia.org/wiki/Quantum_harmonic_oscillator

If you want to know more here is the book to get:

https://www.amazon.com/dp/019969933X/?tag=pfamazon01-20

Thanks

Bill

- #18

bhobba

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Ponderer said:What about the NIST experiment?

Don't know that one.

But if true it would be Earth shattering news comparable to the paradigm shift that occurred early last century. Since that hasn't happened its likely, at the most controversial, and probably wrong.

I suggest you do a separate post about it where people up on that sort of thing can comment.

Thanks

Bill

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Derek Potter

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Ah yes, but "our" theories don't believe in virtual particles - do you? :)bhobba said:They never occur in our theories.

Thanks

Bill

- #20

bhobba

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Derek Potter said:Ah yes, but "our" theories don't believe in virtual particles - do you? :)

And its relevance to actual photons or the question asked is?

Virtual particles are part of the theory. They are in the Dyson series and pictorially represented in Feynman diagrams:

http://bolvan.ph.utexas.edu/~vadim/classes/11f/dyson.pdf

Thanks

Bill

- #21

BiGyElLoWhAt

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In my (and many others') opinions, a quantum of the electric field, or a comparison to a mathematical construct isn't a good definition of a physical entity.

- #22

bhobba

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BiGyElLoWhAt said:In my (and many others') opinions, a quantum of the electric field, or a comparison to a mathematical construct isn't a good definition of a physical entity.

I think you will find most physicists accept the mathematics as the description of reality. But what else would you use? English - it can't be physical reality either.

Thanks

Bill

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newjerseyrunner

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About half way through, he starts talking about how the affects of gravity can be written in three very different ways and be completely equivalent.

Mathematical algorithms can be manipulated so far from their starting point that they don't even look anything like the original anymore, but because of certain mathematical laws, they're still completely equivalent. Someone who needs to use those laws will use the most mathematically simple way.

- #24

bhobba

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newjerseyrunner said:If you are interested in why mathematical models and physical reality can sometimes be so far apart from each other,

I think you will find that Feynman is in the mathematics describing reality camp. It's been a while since I watched that clip, but if I recall correctly Feynman was making the point the laws are written in mathematical language - as all current physical theories are.

Thanks

Bill

- #25

BiGyElLoWhAt

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Of course they are. Physics is about making quantitative predictions, so you need a mathematical model to be able to get said quantitative predictions. This does not mean that the math is the same as the physical entities.bhobba said:I think you will find that Feynman is in the mathematics describing reality camp. It's been a while since I watched that clip, but if I recall correctly Feynman was making the point the laws are written in mathematical language - as all current physical theories are.

That very well may be, but not in my personal experience. I am, however an undergrad, but even my professors would disagree, the chair in particular. I know these aren't really "credible sources" on this forum, but once again, in my personal experience.bhobba said:I think you will find most physicists accept the mathematics as the description of reality. But what else would you use? English - it can't be physical reality either.

English is not what the "stuff" that we're talking about is, whatever it may be (photons in this case). English is what we use to describe it. Math is the same way. It's not what the "stuff" is, it's what we use to describe it.

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bhobba

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BiGyElLoWhAt said:Of course they are. Physics is about making quantitative predictions, so you need a mathematical model to be able to get said quantitative predictions. This does not mean that the math is the same as the physical entities.

The map is not the territory. So?

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Bill

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BiGyElLoWhAt

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- #28

bhobba

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Its a trivially obvious statement that applies to any description of anything. Its basically vacuous because it means you can never know anything - photons, fields, the big bang - anything.

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Bill

- #29

BiGyElLoWhAt

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Perhaps we should just agree to disagree on this point.

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newjerseyrunner

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- #31

bhobba

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newjerseyrunner said:

A virtual photon is just a diagrammatic representation of something called a Dyson series - it doesn't exist - but because of an unfortunate name people who don't know the technicalities get confused. A real photon will register on things like a photomultiplier.

You will find many threads on this forum discussing it - so please don't pursue it here. It is unfortunately one of those things that leads to long threads that go nowhere.

Thanks

Bill

- #32

newjerseyrunner

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I'll look into that, but my mention of it here was simply to illustrate that mathematical entities may not always correspond to actual stuff. I asked it as a question because I wasn't totally sure I was correct. I should have phrased it to make that more obvious.bhobba said:A virtual photon is just a diagrammatic representation of something called a Dyson series - it doesn't exist - but because of an unfortunate name people who don't know the technicalities get confused. A real photon will register on things like a photomultiplier.

You will find many threads on this forum discussing it - so please don't pursue it here. It is unfortunately one of those things that leads to long threads that go nowhere.

Thanks

Bill

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Ponderer

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- #34

bhobba

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newjerseyrunner said:I'll look into that, but my mention of it here was simply to illustrate that mathematical entities may not always correspond to actual stuff.

That's true. Mathematical models can and often do contain things there are no correspondence rules for in the model. An obvious example is, say, minus numbers. You can't have a minus number of ducks for example. But you can owe someone some ducks so it can be given meaning.

The whole area of mathematical modelling in general, and physics is a mathematical model, is full of that. It's so basic its almost, but not quite because novices of a philosophical bent, in an understanding sense, can get confused by it, trivial.

Also, and this is another point those that don't have experience in mathematical modelling and applied math in general, is they read articles from pure mathematics where objects are abstract. The axioms of applied math are not like that - they can, and do, have explicit or implied correspondences with actual things. For example in QM axiomatically it mentions things like observations. Observations are a primitive and actually exist. One can develop QM in a pure math way but the resultant math is - HARD - and is not recommended for the beginner. But just for completeness here is a book that does it:

https://www.amazon.com/dp/0387493859/?tag=pfamazon01-20

Thanks

Bill

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bhobba

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Ponderer said:

The axioms of applied math explicitly or implicitly contain that correspondence. See Euclids geometric axioms compared to Hilbert's as an example. You will find a good discussion on this in Fellers classic on probability:

https://www.amazon.com/dp/0471257087/?tag=pfamazon01-20

Thanks

Bill

Energy levels in hydrogen refer to the specific amounts of energy that an electron can possess while orbiting the hydrogen atom's nucleus. These energy levels are represented by quantum numbers and determine the electron's distance from the nucleus.

The formula for calculating photon energy in hydrogen is E = -13.6/n^2, where n is the principal quantum number. This formula is derived from the Bohr model of the hydrogen atom and represents the energy released when an electron transitions from a higher energy level to a lower one.

The energy levels in hydrogen are directly related to the wavelength of the photon emitted when an electron transitions between them. As the energy level increases, the wavelength of the photon decreases. This relationship is described by the formula E = hc/λ, where h is Planck's constant, c is the speed of light, and λ is the wavelength.

The energy level of a photon in hydrogen can be determined by using the Rydberg formula, which is 1/λ = R(1/n1^2 - 1/n2^2), where R is the Rydberg constant, n1 and n2 are the initial and final energy levels, and λ is the wavelength of the photon. By rearranging the formula, you can solve for the energy level of the photon.

Understanding energy levels in hydrogen is crucial in many fields of science, including chemistry, physics, and astronomy. It allows us to accurately predict the behavior of electrons in the hydrogen atom and understand the properties of light emitted from hydrogen. This knowledge also helps us to better understand the structure of other atoms and molecules and their interactions with electromagnetic radiation.

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