Hi guys, I'm new to this forum... I was just reading the link given below,posted by ZapperZ, describing as how photons propagate in the form of phonons in medium like glass.... https://www.physicsforums.com/showthread.php?p=899393#post899393[/COLOR] [Broken] and a question it struck to me, In the last paragraph ZapperZ wrote that, "On the other hand, if a photon has an energy beyond the phonon spectrum, then while it can still cause a disturbance of the lattice ions, the solid cannot sustain this vibration, because the phonon mode isn't available. This is similar to trying to oscillate something at a different frequency than the resonance frequency. So the lattice does not absorb this photon and it is re-emitted but with a very slight delay. This, naively, is the origin of the apparent slowdown of the light speed in the material." Now my question is if we use a highly monochromatic light of frequency more than the phonon spectrum of glass then, light would transmit through glass by the process of to absorbtion of photons by the lattice and again re-emission and we must get intensity at the end of glass slab equal to the intensity incident.But in reality this does not happen , some energy is absorbed by the slab and we don't get intensity of wave emerging out of slab equal to incident intensity.Why it is so???? Why some photons do get permanently absorbed by the glass plate,even if all of them had energy beyond the phonon spectrum of glass???? Ideally, all the identical photons having energy beyond the phonon spectrum of glass should have been emitted as told by ZapperZ that "if the photon has an energy beyond the phonon spectrum, then while it can still cause a disturbance of the lattice ions, the solid cannot sustain this vibration, because the phonon mode isn't available" and none of them(photons) should have been absorbed permanently by glass slab and we should get 100% intensity on the other side of the slab.But in reality,this doesn't happens,Why????? I think that we cannot explain this absorption of photons with the help of phonon and quantum theory.It can only be explained by classical physics,considering light to have wave nature and not particle(photon) nature.If anyone can clear this doubt of mine with the phonon theory and quantum mechanics,it will be really pleasant and exotic.This question is really nagging my brain and as you see, I am not able to get it on the track with phonon mechanism.Please help by trying to answer my question. Waiting for a sensible reply.