Question

Distinguish between absolute refractive index and refractive index of a medium.

Answer 1

	Absolute Refractive Index	Refractive Index (Relative)
1.	The absolute refractive index of a medium is defined as the ratio of the speed of light in a vacuum to the speed of light in that medium.	The relative refractive index of medium 2 with respect to medium 1 is defined as the ratio of the speed of light in medium 1 to that in medium 2.
2.	n = `c/v`, where c is the speed of light in a vacuum and v is the speed of light in the medium.	`""_1n_2 = v_1/v_2`, where v1​ is the speed of light in medium 1 and v2​ is the speed of light in medium 2.
3.	It always uses vacuum (or air) as the reference medium.	It always uses vacuum (or air) as the reference medium.
4.	The value of the absolute refractive index is always greater than or equal to 1.	The value of the relative refractive index can be greater than, less than, or equal to 1, depending on the pair of media.
5.	It is also simply called refractive index when vacuum is the reference medium.	It is also called the relative refractive index, commonly used when studying the bending of light between two media.