Give the expression for refractive index in terms of speed of light.

In terms of speed of light, refractive index is defined as the ratio of that speed of light in vacuum to the speed of light in medium. n = c/v, where 'n' is the refractive index of the denser medium with respect to air, 'c' is the velocity of light in air and 'v' is the velocity of light in denser medium.