What is Index of refraction?

Refractive Index is the measure of bending of light rays.

Explanation:

Index of refraction or Refractive Index is the measurement of the phenomenon exhibited by light rays - bending of light rays when passing from one medium to another. It can also be measured as the ratio between speed of light in vacuum or empty space to that of the speed of light in a given medium. Index of refraction is denoted by n and is calculated by the following formula

n = Speed of light in vacuum/Speed of light in the given medium = c/v

It can also be measured using the angle of incidence and angle of refraction.

n = sin i/sin r where i is the angle of incidence and r is the angle of refraction