Hi everybody. I had a discussion on another (engineers') forum about the "lower than c" speed of light inside a transparent material (e.g. glass). The explanation that I gave is that the reduction of the light's speed inside such a material is only "apparent" and not "real". The incident photons are absorbed and re-transmitted by the material's atoms (i.e. an atom's electron is stimulated on a higher energy level -via the absorption of the photon's energy- and, right after that, it returns to its fundamental energy level, by transmitting another photon). In this way the light propagates inside this medium. However, between the atoms the light still travels at speed c (because only vacuum exists between the atoms). So, the "lower than c" speed of light inside this medium is caused by the overall delay due to this absorption and re-transmission process by the atoms. So, only the average speed of light is lower than c. Is this explanation correct???