From other answers, I see that the greater the electrical conductivity of a material, the more infrared radiation is blocked. Can anyone tell me why? Thank you very much.
I am no expert on this so take this answer carefully. I think the following idea is the main point. The radiation consists out of electric and magnetic oscillating fields. When the radiation hits the material the electric field interacts with the charges in the material. If you have a conductor the charges in the material move and this creates an electric field counteracting that of the radiation. Hence the electric field reduces i.e. the radiation is blocked. In the case of an insulator the charges aren't free to move and hence can not create an electric fieldto oppose that of the radiation. To find a more mathematical answer you would probably have to solve maxwells equations coupled to the e.o.m.s of a charge in an electric field. I'm not sure how far this is analytically possible.