I must misunderstand, I wasn’t thinking of the “group velocity” (or that “frequency” making light “faster than light”), but plain old slow speed of light!
Like in water, light moves (as for data transfer) slower than in vacuum, right? There are materials that slow down light to a crawl (I read some theory some time ago about slowing down light to almost zero).
So I thought that in some material, x-rays were faster than light, both being slower than c of course.
c is the speed of light in a vacuum. It is impossible to send information faster than c. x-rays are also just light so everything I said before also applies to x-rays.
I’m not very familiar with how light interacts with materials since it wasn’t covered in the electromagnetism class that I took, so the next part might be wrong. The speed of light is calculated by looking at Maxwell’s laws of electromagnetism and recognizing that it is the equation for a wave. The speed is then calculated as c = 1/sqrt(epsilon_0 * mu_0) where epsilon_0 and mu_0 are the vacuum permittivity and the vacuum permeability. Inside a material, I think the permittivity and permeability are different and thus the speed of light as determined by Maxwell’s equations would be different. I know its not possible for the speed (group velocity) of light in a material to be faster than the speed of light in a vacuum because otherwise, you could send information faster than c, which is impossible.
Yeah we all know that (don’t remember that function but if you say so, tje one I was taught was for sure simpler), but the question is not if light can be made to move slower (or over c) but if it moves slower than another electromagnetic radiation like x-rays in some specific material.
I dunno about xrays, but it is true that light slows down in media and that particles can move faster than light in that medium, that’s where Cherenkov radiation comes from! (Though I’m not sure if that also just slows down the particles or what)
I must misunderstand, I wasn’t thinking of the “group velocity” (or that “frequency” making light “faster than light”), but plain old slow speed of light!
Like in water, light moves (as for data transfer) slower than in vacuum, right? There are materials that slow down light to a crawl (I read some theory some time ago about slowing down light to almost zero).
So I thought that in some material, x-rays were faster than light, both being slower than c of course.
c is the speed of light in a vacuum. It is impossible to send information faster than c. x-rays are also just light so everything I said before also applies to x-rays.
I’m not very familiar with how light interacts with materials since it wasn’t covered in the electromagnetism class that I took, so the next part might be wrong. The speed of light is calculated by looking at Maxwell’s laws of electromagnetism and recognizing that it is the equation for a wave. The speed is then calculated as c = 1/sqrt(epsilon_0 * mu_0) where epsilon_0 and mu_0 are the vacuum permittivity and the vacuum permeability. Inside a material, I think the permittivity and permeability are different and thus the speed of light as determined by Maxwell’s equations would be different. I know its not possible for the speed (group velocity) of light in a material to be faster than the speed of light in a vacuum because otherwise, you could send information faster than c, which is impossible.
Yeah we all know that (don’t remember that function but if you say so, tje one I was taught was for sure simpler), but the question is not if light can be made to move slower (or over c) but if it moves slower than another electromagnetic radiation like x-rays in some specific material.
I dunno about xrays, but it is true that light slows down in media and that particles can move faster than light in that medium, that’s where Cherenkov radiation comes from! (Though I’m not sure if that also just slows down the particles or what)
Fascinating, thanks for the info!