If I understood Wikipedia correctly then light that travels through a transparent material gets absorbed by it and then reemited. Does the material remember from which direction the light came? Sounds unlikely. I guess this is were light being a wave comes into play.

Also I guess the absorption and reemiting has to be instantaneous otherwise if if some atom absorbed two photons in short enough succession it would emit one photon that combines the energy of both or keep track somehow.

But if it is instantaneous how then do transparent materials manage to slow down the light traveling through it?

That was my original question and somehow I didn& #39;t manage to answer it even though I totally thought I had when I was writing the first tweet in this thread.