# Refractive index Formula

Refractive index on the basis of speed of light.

1) Refractive index of medium 1 with respect to medium 2 is defined as the ratio of speed of light in medium 2 to the speed of light in medium 1, written as,

2) Refractive index of medium 2 with respect to medium 1 is defined as the ratio of speed of light in medium 1 to the speed of light in medium 2, written as,

3) Absolute refractive index of medium is defined as the ratio of speed of light in vacuum (or air) to the speed of light in the given medium, written as,

Ex.1) If absolute refractive index of diamond is 2.42, find the speed of light in diamond.

Solution: Data given;

Data given;

Absolute RI of diamond, μ=2.42

Speed of light in vacuum = 3×10^8 m/s

Formula:

On substituting we get,

Ex.2) A ray of light is travelling from water to glass slab where velocity of light in water is 2.25 ×10^8 m/s and that of glass is 2.00 ×10^8 m/s. Find Refractive index of 1) glass with respect to water, 2) water with respect to glass.

Updated: April 28, 2021 — 4:27 pm