Hello Guys! I have been studying electromagnetic waves (EMW) interaction with matter lately and I just derived the results for the propagation of EMW inside linear media and perfect conductors. As it turns out, when a plane EMW changes medium (at a normal incidence) from air to (good) electrical insulators most of the EMW is transmitted (thus glass is transparent) and when going from air to (good) conductors most of it is reflected (thus metals are opaque and when polished are good mirrors). So I cannot help but wonder why aren't more materials transparent? Wood, paper, all these things that are good insulators are opaque as well. Well, I know that this is an incomplete picture since it considers the EMW as plane and homogenous and does not take into account microstructure and quantum effects that arise from more accurate matter description. I believe one of the main processes that render opaqueness to most insulator materials is due to non-normal incidence of light into granulated matter that scatters off in all kinds of complicated ways that make them opaque. For example, ice is transparent when it is fabricated in such way as it is nearly a monocrystal but it looks white when it has a granulated (policrystalline) structre (walls of your freezer). If we could fabricate insulators such as rubber or most ceramics in a homogenous way would they be transparent to visible light? I believe the the usual lack of homogeneity and granularity of most materials make them opaque but common glass or quartz (SiO2) is amorphous and is still transparent...so why aren't more insulators transparent? Thanks for reading... sorry if this post sounds confusing...it was written by a confused mind hehe.