B Reflection of light from the mirror

[Vrbic]

What is exactly happening when the light hit a surface of a mirror? I know it is not same as a bounce of ball from the wall, because of constant speed of light for example. So I suppose the light is absorbed by electron of reflecting material. This probably define the materials who are appropriate - energy between valence electron level and some higher level has to be in accordance with energy of visible photon.
Am I right?
I also realize that photon is absorbed and emited (lines in spectrum), but I would expect izotropically emitting (to all directions). How is possible that photon is "reflected" exactly in same direction back if comes perpendicular?

 

[vanhees71]

It is way better to think about light in terms of good old classical electrodynamics (aka Maxwell's equations) than to think about photons as a kind of massless "billiard balls". Photons are far from what we'd consider as particles. E.g., there's no way to define a position observable for them.

Looking from the field-theoretical point of view, what happens is that an electromagnetic wave hitting the surface of a good conductor is that it starts to rattle the free charges (in metals these are electrons), which emit an electromagnetic wave. After some time a stationary state results, and the superposition of the external wave field and the field due to the accelerated charges (close to the surface of the metal (skin effect)) leads to the usual description in terms of Fresnel's formulae, which follow much simpler from considering plane-wave modes of the em. field and the boundary conditions on the surface of the conductor. For an excellent treatment of the above mentioned more macroscopic point of view, see

Melvin Schwartz, Principles of Electrodynamics, Dover Publ. 1972

 

[BvU]

Hi,

Good question. Answer on many levels of complication can be given.
I'll recount here what worked for me (experimental physicist):

Light is an electromagnetic wave. If it bumps into a conductor you get boundary conditions and to satisfy those the equations lead you to this reflection business. For media with a different speed of light you get the refraction laws too.

(Can't wait for the real experts to pound on this simplification

[edit] but I didn't expect one of them would be so quick as to beat me to it!
[edit2] this way PF starts to look like a mutual admiration society ​

So I suppose the light is absorbed by electron of reflecting material.

Note that the wavelength of light is much bigger than the dimensions on an atomic scale. So the reflecting medium can be considered as (almost) a continuum. Much easier on the math.

 

[Vrbic]

Hi,

Good question. Answer on many levels of complication can be given.
I'll recount here what worked for me (experimental physicist):

Light is an electromagnetic wave. If it bumps into a conductor you get boundary conditions and to satisfy those the equations lead you to this reflection business. For media with a different speed of light you get the refraction laws too.

(Can't wait for the real experts to pound on this simplification

[edit] but I didn't expect one of them would be so quick as to beat me to it!
[edit2] this way PF starts to look like a mutual admiration society ​

Much easier on the math.

Thanks for comment and summary.

Note that the wavelength of light is much bigger than the dimensions on an atomic scale. So the reflecting medium can be considered as (almost) a continuum. Much easier on the math.

I understand that analogs in macroscopic world aren't much appropriate, but :-) May I imagine it such:
I have a cube of jelly in the water. Where water is electromagnetic field and jelly are atoms (electrons) of mirror. When a wave hit a face of jelly it demorms a bit and in a moment it relaxs to get ordinary state and create backward wave (in same direction it came from).
Is it a bit right view?
I believe it is possible to calculate quite exactly what is happening. But by some approximation. I am not looking for math but phenomenons of physics which are present while is light reflected from the mirror.