When light is reflected something happens - they say light gets polarized. Well, that is easily demonstrated with sun glasses. But I don’t see anything happening to that damn photon. Will you explain me?
Warning: here be Quantum
Simplest case: You have a beam of light, and it hits a polarizing transmission filter. If the beam of light already has the right kind of polarization for the filter, then all of it gets through. If it doesn’t already have the right polarization, then some of the photons (the ones that have the right polarization) pass through, and some of them (the ones that have opposite polarization) will get absorbed or reflected. What proportion is absorbed or reflected can be calculated based on the filter and the polarization of the incoming beam. And the quantum-weird part is that no matter how you set up your filter, some of the individual photons will turn out to have had exactly the right polarization, and some of them will have the polarization exactly opposite of that, with none ever being any other polarization.
I think the OP was asking what polarization means when light is considered as particles, since usually polarization is thought of as a wave phenonemon.
It can be thought of as a particle phenomenon, too, with very little difficulty: It’s closely related to the spin of the particles. In fact, circular polarization is exactly the same as the spin of the particles being aligned in either the same direction they’re moving, or the opposite direction. Linear polarization in terms of spin is only a little more complicated, provided that you’re comfortable with complex numbers.
Wait. Why? I mean, I’m assuming there’s more than two kinds of polarization, because otherwise, that wouldn’t be weird. Do the light particles change their polarization when they hit the filter?
What if you have two different filters? Lets say you have a filter with polarization A, of which the opposite is polarization B. So then you shine the light through that and all the A photons pass through and the B photons are rejected. Then you put, after that, the filter with polarization C of which the opposite is polarization D? What happens to the photons?
I suspect the right question is the three filter experiment.
Put two filters in line, one horizontal polarisation, the other vertical. Within the bounds of the quality of the filters, no light comes though. Now put a filter aligned at 45 degrees to the existing filters, between them. Conventional description of action of polarisors suggests that still no light should come through. But suddenly light does. Put the 45 degree filter last (or first) in the chain, no light. But in the middle light does. This has a very clear implciation for what a polariser does.
This site’s explanation of the three-filter experiment makes sense to me, but then again I am part of the ignorant rabble when it comes to these matters. Is this a valid explanation of what’s going on with polarized filters?
That’s a perfectly valid explanation when it comes to waves, and in fact you can demonstrate something like that with waves on a string and picket fence filters. But the OP was asking about individual photons, particles. The net result is the same, but the wave explanation doesn’t work for things we think of classically as particles.
The full explanation is that light is waves and light is particles, and it’s that duality that makes it inherently quantum mechanical.