Why does light slow down in materials with high refractive index?

Question

My understanding of relativity is that the speed of light is invariant in all reference frames, so how is it that light can slow down while it is in a high index material and speed back up when it exits the material while I remain in the same reference frame?

I recently asked 2 professors of optics about this. What I found is that individual photons do not slow down in a medium, but their interaction with the EM field of the medium causes them to be absorbed, and re-emitted. It is the mass in the electrons that requires time for them to accelerate when they interact with photons, and this is what 'slows down' light.
I'm going to look into this more, for instance, I'm curious if a neutron can propagate through a material faster than a source of light would.

Answer 1

That's a common misconception. Einstein only did his calculations with the speed of light in a vacuum, with no outside interactions. Once light enters a medium, the electric and magnetic fields associated with the photon (that's why it's called electromagnetic radiation) interact with the fields associated with the electrons and protons in the atomic structure. This interaction slows the light down, similar to the way air slows down a projectile (well, not really similar - the physics are very different - but it works as an illustration). Where relativity comes into play, in this case, is that, no matter what the speed of light within the medium, nothing else can go faster than that. So if light slows down to 3/4 c in a medium with a high index of refraction, nothing else can go faster than 3/4 c in that medium either.

Answer 2

Light does not slow down. It takes a long time to EXIT the material. Hence it is perceived as going slower, from point A to point B. Look at it this way. You are traveling in a car, at 100 mph. You never slow down. You are always going at 100 mph. But then you hit a maze. It takes you an hour to get out of the maze, though the maze is only a mile long. So, it takes you 2 hours to travel 100 miles, instead of an hour. But you were always traveling at the same speed. It is the same with light. In a medium with high refractive index it keeps spinning around in the medium until it exits. Hence it seems to slow down.

Answer 3

mild does decelerate fractionally whilst traveling via sparkling drinks..to coach this positioned some water in a bowl...then basically positioned a stick in at an perspective you will see that the stick seems to bend..it relatively is as a results of the fact the sunshine falling on the stick in the process the water is back on your eyes at diverse speeds.because it is going deeper in the water to return...additionally diverse colorations trip at diverse speeds ..white mild travels at one hundred twenty five,000 miles in line with 2nd..or around the earth 7 cases in one 2nd..i'm basically waitng for some-one to split a photon..then in line with danger we are able to understand time...