From the school physics I know that the material objects bounce from the plane surface at the same angle, losing some kinetic energy. In the same school I was taught that the light (and waves in general) obeys this principle too.
Obviously, in the case of light the plane surface should be a perfect mirror. But I can't understand how should this work from the quantum point of view. Let's assume that our mirror consists of a single silver atom.
Why should the electrons of this atom re-emit consumed photons at some specific angle?
Answer
That's a good question. Without realising it you have stumbled across the Huygens-Fresnel principle.
The starting point it that a single silver atom is far smaller than the wavelength of light, so any scattering from it will be isotropic i.e. it will scatter the light equally in all directions.
But suppose we have two silver atoms side by side. Each atom will scatter isotropically, so in effect we have two closely spaced emitters of light and the system behaves like a Young's slits setup. Now the light isn't simply isotropically scattered, but instead it's scattered into preferred directions. (I'm oversimplifying because two atoms would be too closely spaced to act as Young's slits, but bear with me.)
Now add lots of atoms in a row, and you get something like a diffraction grating. Add lots more to make a 2D surface, then add more layers of silver atoms below, and you're building up a system where the overall light scattering is the sum of individual scattering from huge numbers of individual silver atoms. This is basically the Huygen's construction, and if you do the sums for a surface you can show that the overall scattering is only non-zero when the angle of reflection is equal to the angle of incidence. Any optics textbook should have the calculation, or a quick Google found an example here.
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