Originally posted by Integral
If you look through the fourms you will find many threads addressing the propogation of light through a medium. In reality light does not "slow down" in water. Up on intering the water a photon is adsorped by a water molecule leaving the molecule in an excied state. A short time later a photon is reemitted. Each emission is in a random direction, perhaps with some favor in the original direction due to momentum consideraions.
The net effect is a delay in the passage of a photon through a medium, this delay depends on the atomic structure of the medium, thus differing index of refractions.
There are two things that bother me about the reemission idea.
The first is that the reemission has to be in discrete frequencies. So you'd think that many atoms together cause degeneration so that essential any frequency (say in the visible range) can be emitted.
Ok so far but what about thin films? There might be only a few atom layers thick. Can you still get essentially any frequency out that came in?
Second thing is wouldn't some photons get lucky and avoid hitting any atoms at all? Then there would be no slowing down at all and you would get 2 speeds for photons, one fast and one slow. Has this been observed?
If this belongs in another thread feel free to move or ask me to start one.
I will buy QED but I won't be able to read it until Dec so I hope you can address these issues now.