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We all know that light is reflected from mirror but my question is that what happens at Quantum level when the process of reflection is happening?

does the photon first get absorbed and then re-emmited from surface of mirror or is the photon just bounce from the surface?

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  • $\begingroup$ There are similar questions on this site that you can search. Your question is a very good one and you can learn a lo about physics from it. (but the visible photon is not absorbed .... using the physics definition of absorption) $\endgroup$ – PhysicsDave Dec 9 '18 at 3:33
  • $\begingroup$ Compton Scattering in a mirror is mediated by a virtual electron between the events of absorption and reemission. The best answer is here, but it is not simple: physics.stackexchange.com/questions/368333/… $\endgroup$ – safesphere Dec 9 '18 at 8:04
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Photons get absorbed, then the atoms re-emit them. I can get more into the details but it difficult to understand without some knowledge in QM. In one sentence I would say that the frequency of visible light matches with the energy needed to excite the atoms.

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  • $\begingroup$ You are correct that a photon is absorbed and reemitted, except not by an atom, so the atomic energy levels are irrelevant in a mirror. Photons in a mirror interact with free electrons in the process of Compton Scattering (or its low energy version). $\endgroup$ – safesphere Dec 9 '18 at 8:05
  • $\begingroup$ @safesphere That is wrong. Compton scattering is an inelastic process while mirroring is elastic. $\endgroup$ – my2cts Dec 9 '18 at 10:06
  • $\begingroup$ @hanting zhang Please provide a reference for this explanation. This has been said many times on this site and never a reference was produced to support the idea. $\endgroup$ – my2cts Dec 9 '18 at 10:10
  • $\begingroup$ @my2cts Any scattering of two elementary particles is elastic, because elementary particles don't have internal energy levels to take energy away from motion, as required for an inelastic process. Perhaps what you really mean is not "elastic", but the change in the energy of the photon. At low energies this change in the Compton scattering is negligible. Read the first paragraph here: en.m.wikipedia.org/wiki/Thomson_scattering - In addition, electrons in a mirror are not free particles in free space, so the process is more complex, but it still is photon scattering on electrons. $\endgroup$ – safesphere Dec 9 '18 at 17:07
  • $\begingroup$ @safesphere So you meant Thomson scattering, not inelastic Compton scattering. Nevertheless, Thomson scattering does not apply either, since we are discussing interaction with a mirror and internal degrees of freedom thereif, which by no stretch of words is a "free charged particle". $\endgroup$ – my2cts Dec 9 '18 at 19:40
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The photon elastically scatters off collective electronic states of the solid. These can be optical phonons or plasma resonances.

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