Gravitational force affected by refraction?

[Rlam90]

So I understand that light "slows down" in a refractive medium. This obviously would increase the density of photons within the medium. Also, from what I understand, photons do contribute slightly to the effects of gravity.

Now, suppose we take two purely theoretical mediums of equal volume and shine light of equal intensity through them both. One of the mediums is more refractive than the other, but both have equal mass. Would the more refractive medium therefore contain more photons and as a result produce higher gravitational forces than the other?

This raises another question: does the gravitational force of individual particles have anything to do with some form of energy being refracted within or around the particles? Say particles with a greater mass refract more of this energy within or around themselves so that their energy density would be higher. What form of energy would this be?

Bear with me, I have no official education in any field of physics. I study what I can understand in my spare time.

 

[soothsayer]

Yes, if a stream of photons pass through two mediums with different optical densities, there would be more photons in one of the mediums, and it would increase the gravitational field from it by a very tiny amount.

Photons generate a small amount of gravity by contributing to something called the stress-energy tensor, an idea from General Relativity

http://en.wikipedia.org/wiki/Stress-energy_tensor

This may be what you were referring to as "energy refracted within or around particles themselves" in a way.