Is the speed of light in glass independent of the colour of light? If not, which of the two colours red and violet travels slower in a glass prism?

Speed of light in glass is dependent on the colour of light as different colours have different wavelengths, thus different velocities.

We know that refractive index of a material in terms of the wavelength of light is

μ = a + (b/λ2)

As the wavelength of violet light is smaller than that of red light,

μv > μr.

We also know that


vv < vr

Hence velocity of violet light in glass is less than velocity of red light.