Question

define absolute refractive index

Answer 1

The refractive index of a material with respect to vacuum is called as the absolute refractive index of that material. It is constant. e.g. air has an absolute refractive index of 1.003, and diamond has 2.42.

Answer 2

Absolute refractive index is a number indicating light's speed in a given medium as the ratio of the speed of light in a vacuum to that in the given medium