3 ms·
Well ... no. The value of c is specific to the medium. In "empty" space, c is the constant we know and love, and is related to the permittivity and dielectric
by hpcjoe 9y ago
Well ... no. The value of c is specific to the medium. In "empty" space, c is the constant we know and love, and is related to the permittivity and dielectric constant of the vacuum.
Specifically with a classical E-M model, when you are in a material different than vacuum, the differing dielectric and permittivity of the material are (in a macroscopic sense) what lead to the reduced c*. This is encapsulated in the form of the index of refraction, which is effectively the ratio of velocities between vacuum and in-bulk.
At a microscopic E-M quantum level, you can argue about vacuum state differences between physical vacuum and in-bulk. Indeed, in a physical vacuum, you have virtual pair creation/destruction, virtual photons, etc. In bulk, you may have that, but you also have the bulk electronic and physical structure to work with, as well as different fields and field structures.
- kgwgk 9y ago> The value of c is specific to the medium. c is the speed of light in vacuum, a universal constant that obviously doesn't depend on the medium.
- whatshisface 9y agoSometimes people write c with subscripts, so I've seen the notation he's using before. It sounds reasonable enough to me. Edit: To be specific, in this context c was used for the speed of light in the medium and c_0 for the speed of light in vacuum. (To match epsilon and epsilon_0).
- kgwgk 9y agoHave you seen c being used to refer to something else than the speed of light in vacuum in a discussion about the interaction of photons with matter? Edit: yes, I know. But using c in that way is absolutely non-standard in physics (v is used instead). Actually he later used c* for the speed of light in a medium, so he knows what c is.