Few, if any elements are transparent in solid form, but quite a few solid compounds are transparent, so perhaps we should say the light is absorbed by a molecule (silicon dioxide instead of an atom) To keep images intact, the light needs to be emitted out the opposite side of the molecule, with the same yaw, pitch and elevation. Or so it seems to me. The re-emission delay is about one picosecond, varying with the molecule and the photons wave length, and the path length = Not too believable: Is there an alternate theory on the transparency of solids? Neil