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So, as far as I understand, white light contains photons of all energy levels. These hit a material, say iron. The photons that are below the energy level to move electrons just pass through. The others deflect the electrons to another orbit and when the electrons go back to their original orbit, they emit a photon.

Is that the case?

If so, I can understand why a material will emit a certain color back. These are the photons emitted back. But, what happens to the photons that just passed through? Why don't I see the complement color from the other side of the iron? Is it because they too get absorbed and turn to infrared level photons? If so, how?

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Solid materials are composed out of an enormous number of atoms,organized in a lattice, i.e. the atoms are bound to each other in electromagnetic energy levels and collectively have a surface field which can interact with the incoming photons.

Classical waves have reflection, where the color composition is intact, as in mirrors and shiny surfaces. This means that the photons which build up the classical light beam scatter elastically with the surface lattice field without changing frequency, and thus the colors in the reflected image are unchanged.

On non reflecting surfaces, i.e. where there is absorption of classical light, color perception plays a role. Photons interacting inelastically, either with the whole lattice, or with particles made up by different tiny crystals with various orientations , will either give up all their energy increasing the lattice vibrations, or, few of them penetrating to the atomic level will be absorbed in raising atomic energy levels, (which deexciting will finally release the energy to vibrations of the lattice, heat) .

The color reflected from the surface then goes into color perception..Depending on the material the reflected frequencies to our eyes will give the color our retina detects, as in the link.

In transparent materials photons may go through the whole lattice interacting elastically with it, and thus not changing frequency. In non transparent materials the absorption happens at the surface, inelastically and close to the surface eventually turning into infrared photons.

All the above is qualitative. Classical theory explains well the behavior of light and it is only in special research subjects that the behavior of the individual photons has to be checked.

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