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I am looking for a physical electrodynamic explanation as to why when a beam of randomly polarized light is incident on a filter, (for example a sheet of polyvinyl alcohol molecules embedded in a polymer film which is stretched and doped with elemental iodine), why certain oscillatory permutations of photons can be absorbed by this chemical sheet and some are not absorbed and can pass through. I assume the explanation has to deal with the oscillating electric and magnetic fields of the photons of light (probably the electric component) exciting electrons so they can be absorbed. I don't know why the orientation of the oscillating fields should matter then in the excitation of electrons in the molecules. Also, why should then, when a filter is applied, we see diminishing light intensity because should the absorbed light not be reemitted as the electrons relax to a ground state? Is this latter question's answer to do with Stoke's shift? If QM is necessary to explain this don't hold back... I would rather get a complete and thorough answer to digest, but if possible include the big picture along with such responses please.

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    $\begingroup$ The light-absorbing molecules in a Polaroid filter become oriented primarily along the direction of stretching. Because electrons can easily move in the direction in which the molecules are oriented, light is strongly absorbed when the electric field vector is aligned with that direction. The absorbed light is not re-emitted because the absorption is not a simple excitation process. The energy of the absorbed light is converted to heat. $\endgroup$ – S. McGrew Jun 12 '18 at 22:03
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    $\begingroup$ Note that there are other kinds of polarizing filters that work in an entirely different way. For example, a stack of glass plates tilted at Brewster's angle toa light beam transmits linearly polarized light of one orientation and reflects the other. No quantum mechanics required. $\endgroup$ – S. McGrew Jun 12 '18 at 22:06

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