Speed of light question.

[knox_122]

Take light in glass. What could slow it down. I know that stuff is asorbed and then reemmited, but what about imperfections in the glass its self?? Say you have a piece glass that has impurities(little defects), or the desity of glass(not optical), the actual wave length of light, or for giggles the how bright the light is??? Would any of these affect the speed of light or would light simply travel around them???

[Danger]

None of those things (indeed, nothing) will affect the speed of the individual photons.

[knox_122]

Well not nothing. The refractive index of a medium will decrease it. Right? The speed of light in glass is slower than in a vaccum. Right??

[ZapperZ]

Danger said the speed of "photons".

The "speed of light" that you are indicating is the GROUP VELOCITY in the medium. This is the speed that is affected by the normal dispersive medium.

Zz.

[Danger]

No, the speed of the photons doesn't change. Sorry... I thought that you knew that from the wording in your first post. It's the absorbtion/re-emission rate, and therefore the propogation speed, that changes with the medium.

edit: Ooops! Didn't see you sneak in there, ZZ.

[ZapperZ]

No, the speed of the photons doesn't change. Sorry... I thought that you knew that from the wording in your first post. It's the absorbtion/re-emission rate, and therefore the propogation speed, that changes with the medium.
edit: Ooops! Didn't see you sneak in there, ZZ.

Didn't mean to speak on your behalf there, Danger. But I wasn't sure if you were around to respond.

Zz.

[Danger]

Hey ZZ, you guys are the experts. I'm always hoping one of you will show up and give a definitive answer. I consider myself sort of a filler-of-space so the kids don't feel neglected before you arrive.