Speed of light maybe not constant after all!:

Originally posted by twhitehead
Yes, I do realize that. It just that I have not heard of the two slit experiment with radio waves so I am having trouble reconciling the two.

[b]Why is it hard to reconcile this with quantum mechanics?
In quantum mechanics a particle is a probability wave of where it will be. But it will always be somewhere.
When you do the two slit experiment, a ...[text shortened]... the two beams are polarized in different directions then there will be no interference pattern.[/b]

The indistinguishability of identical particles is an important concept in quantum mechanics. Indeed, it's what's stopping you from falling to the center of the Earth.

Originally posted by KazetNagorra
The indistinguishability of identical particles is an important concept in quantum mechanics. Indeed, it's what's stopping you from falling to the center of the Earth.

Very interesting.
Presumably photons with different energies are distinguishable, so can this interference happen if the energies are different? Is energy equivalent to wavelength with photons? Is there an infinite possible range of wavelength/energy in photons or is it quantized?

Originally posted by twhitehead
Very interesting.
Presumably photons with different energies are distinguishable, so can this interference happen if the energies are different? Is energy equivalent to wavelength with photons? Is there an infinite possible range of wavelength/energy in photons or is it quantized?

Photons are not distinguishable.

The energy of a photon is proportional to its frequency (the proportionality constant is Planck's constant). However, due to Heisenberg's uncertaintly principle, the energy of a photon is never precisely determined (in a mathematical sense, a precisely defined wavelength corresponds to a photon being defined over an infinite time interval). The possible wavelengths are not quantized AFAIK, though this question may boil down to whether space and/or time are quantized or not.

Originally posted by KazetNagorra
Photons are not distinguishable.

The energy of a photon is proportional to its frequency (the proportionality constant is Planck's constant). However, due to Heisenberg's uncertaintly principle, the energy of a photon is never precisely determined (in a mathematical sense, a precisely defined wavelength corresponds to a photon being defined over an i ...[text shortened]... d AFAIK, though this question may boil down to whether space and/or time are quantized or not.

So, if I understand you correctly, a radio wave photon could strike a screen as a light photon and vice versa in very rare circumstances?
Would they also only interfere in very rare circumstances?
So for interference patterns we need light with very similar, but not necessarily exact wave lengths.
So when two photons from two sources strike a screen it may be impossible to tell which came from which source, and when that happens we get an interference pattern.

So back to refraction and the speed of light.
A photon is absorbed then by either an atom or the bonds between atoms (I don't think I have a definitive answer yet), and then moments later a new photon gets emitted in all directions.
However, the new photon interferes with other photons creating an interference pattern such that the photon appears to have been emitted in the direction of the original photon.
Does this seem right?

Now to crack reflection. I bet it too has to do with interference.

Originally posted by twhitehead
So, if I understand you correctly, a radio wave photon could strike a screen as a light photon and vice versa in very rare circumstances?
Would they also only interfere in very rare circumstances?
So for interference patterns we need light with very similar, but not necessarily exact wave lengths.
So when two photons from two sources strike a screen it ...[text shortened]... ible to tell which came from which source, and when that happens we get an interference pattern.

So, if I understand you correctly, a radio wave photon could strike a screen as a light photon and vice versa in very rare circumstances?

Yes.

Would they also only interfere in very rare circumstances?

It's not a matter of interfering or not interfering, it's a matter of how much they interfere. A radio wave and a visible light wave interfere little.

So for interference patterns we need light with very similar, but not necessarily exact wave lengths.

Exactly. This is what is meant by coherence (and you can replace "light" by "any wave phenomenon" ).

So when two photons from two sources strike a screen it may be impossible to tell which came from which source, and when that happens we get an interference pattern.

Yeah, although the interference pattern does not depend on the screen, the screen is just a way of measuring it.

Originally posted by twhitehead
So back to refraction and the speed of light.
A photon is absorbed then by either an atom or the bonds between atoms (I don't think I have a definitive answer yet), and then moments later a new photon gets emitted in all directions.
However, the new photon interferes with other photons creating an interference pattern such that the photon appears to ha ...[text shortened]... n.
Does this seem right?

Now to crack reflection. I bet it too has to do with interference.

Refraction can be described quite easily using classical mechanics. The laws of refraction have been known for a very long time.

http://en.wikipedia.org/wiki/Snell%27s_law

For some info on reflection and the reason why the sky is blue:

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

Originally posted by KazetNagorra
Refraction ....

I am talking about reflection not refraction. When light reflects off a mirror, are the photons absorbed and re-emitted, or do they 'bounce'? I am guessing the former, and that the angle that they are re-emitted is a function of their interference with incoming photons. This makes me wonder whether single photons can reflect off a silvered surface, and if so, are they interfering with themselves despite a tiny time delay.

Originally posted by KazetNagorra
http://en.wikipedia.org/wiki/Rayleigh_scattering

Am I correct that when light goes through glass it is absorbed and reemitted causing it to apparently slow down, but no scattering occurs, whereas in a gas, the absorption and re-emission is so dispersed that only bits are slowed down which is what results in Rayleigh scattering? So the difference between shallower water (causing shorter wavelengths) and rocks poking up from the surface.

Originally posted by twhitehead
I am talking about reflection not refraction. When light reflects off a mirror, are the photons absorbed and re-emitted, or do they 'bounce'? I am guessing the former, and that the angle that they are re-emitted is a function of their interference with incoming photons. This makes me wonder whether single photons can reflect off a silvered surface, and if so, are they interfering with themselves despite a tiny time delay.

Absorption and (immediate) re-emission would be indistinguishable from "bouncing".

Originally posted by twhitehead
Am I correct that when light goes through glass it is absorbed and reemitted causing it to apparently slow down, but no scattering occurs, whereas in a gas, the absorption and re-emission is so dispersed that only bits are slowed down which is what results in Rayleigh scattering? So the difference between shallower water (causing shorter wavelengths) and rocks poking up from the surface.

I'm not sure I understand your question.

Originally posted by KazetNagorra
Absorption and (immediate) re-emission would be indistinguishable from "bouncing".

But is it immediate? If light is slowed when going through glass, is it also slowed when bouncing off a mirror?
And if it is re-emitted, why is it only re-emitted on the 'air' side of each surface atom and not re-emitted further into the solid?

Originally posted by twhitehead
But is it immediate? If light is slowed when going through glass, is it also slowed when bouncing off a mirror?
And if it is re-emitted, why is it only re-emitted on the 'air' side of each surface atom and not re-emitted further into the solid?

Doppler cooling works from the principle that in re-emission, the direction of emission is random.

Originally posted by KazetNagorra
Doppler cooling works from the principle that in re-emission, the direction of emission is random.

Thanks for all the info, its been quite an education. I think I need to get a book on the subject.

Originally posted by twhitehead
Thanks for all the info, its been quite an education. I think I need to get a book on the subject.

I don't know how far you want to delve into quantum mechanics, but as an undergrad we used Griffiths' book Introduction to Quantum Mechanics. If you really want to get some intuition into quantum mechanical concepts, it's a good place to start. You would need some basic calculus and knowledge of simple differential equations to handle it.