Before you treat this question quantum-theoretically, which involves the propagation of photons in matter, i.e., you have to calculate the photon-polarization tensor in finite-temperature quantum field theory, you should look at the classical theory, how the dielectric function (more generally tensor) is evaluated within simple classical models of matter. The final outcome is amazingly close to the quantum treatment.
1. No, of course not. QFT is a big monster!
2. Thanks, I like hyperphysics! I used to read this site frequently a couple of years ago.
I already found the answer by Google on this site with useful links in someone's answer: