Hi, I'm an undergraduate physics student and I'd like to know more about interactions of light with matter. Since I haven't studied Quantum Physics yet, I'd like to know what happen on a microscopic scale, when e-m radiation passes through a material (transmission), when it's reflected/scattered and when it's absorbed. For example, glass is in general transparent to visible wavelengths, but it's opaque to ultraviolet or infrared. Does that mean that visible wavelengths, unlike ultraviolet and infrared, are not in the specific range to excite electrons and bring them to another orbital? Hope this picture helps: http://img135.imageshack.us/img135/4940/unexcited.jpg [Broken] This is just what I thought can happen. Furthermore, is there any relation between polarization and transmission? About reflection, I supposed e-m is absorbed by atoms in the material and then are re-emitted at the same angle of incidence. Then why not all materials reflect radiation with the same angle of incidence (scattering)? About absorption, why a material should absorb radiation and transform it in internal energy instead of reflecting it? I'm sorry for the poor language, but I've done the best I could do, since English is my second language. I thank so much anyone that try to clarify what's going on when radiation encounters matter.