What materials slow light waves down? Does it have to do something with the density? Please help me understand, medals will be given.

Question

What materials slow light waves down? Does it have to do something with the density? Please help  me understand, medals will be given.

anonymous · Answer

Wait, I know the answer, but it's more of a general physics question. However, you can use some imagination. Light are light tiny particles that travel in a wave-like motion. They collide with atoms, and other particles, interact with their energies/mass. So, if light travels in space (ideally a vacuum), it will be at its fastest. If light travels in air, it'll be a little slower. How about medium that is denser, such as water? Even slower. What about crystals that have closely packed atoms? Even slower.

wolfe8 · Answer

http://openstudy.com/users/wolfe8#/updates/52d882fae4b02397b18dcf5f This is what I just helped someone with. Same question.