The Speed of Light: Variance in Non-Vacuum Mediums

[brainyman89]

Does the speed of light vary with different frequencies(or wavelengths) in mediums other than vacuum, or is it constant for all light regardless the frequency?

 

[Simon Bridge]

When we are talking about the speed of light in a material, we are talking about the refractive index.
The refractive index does depend on the wavelength - yes.
http://en.wikipedia.org/wiki/Refractive_index#Dispersion

Note: light does not move in a medium.
... glass, for eg, does not act as a medium for light when the light is passing through it in the same way as water, string and metal can act as different mediums for sound waves.