does speed of light changes?????

[kamil]

O ok, thx a lot guys, now i understand

[HydrogenBond]

When light passes through a refracting medium, the speed of light remains the same. What is happening is the light is taking time to smell the roses, so to speak. But between roses it is going at C. The extra distance it travels in refracting mediums is a reflection of how long it smells the roses. Diamonds appear to smell better to light than water as reflected by its higher refractive index.

[Qfwfq]

This is a cute analogy of the well-known interpretation of field theory.

It should be however said that it shouldn't be taken too literally, it doesn't make too much sense to distinguish between the photon "going the roses" when the distances betwen them is small compared with the wavelength. As usual, quantum descriptions can't be so blithely translated into classical intuitive notions. The interactions between photon and atoms are usually soft (when they aren't, it's a scattering event and that's a different kettle of fish) and all the absorbtions and re-emissions are only "kinda meta-happening", it's a semi-classical description of something that isn't classical at all.

If the lense can focus most of the light according to wave optics, then the potons aren't really quite getting absorbed and re-emitted by single atoms.