Question

Define refractive index??​

Answer 1

In optics, the refractive index or index of refraction of a material is a dimensionless number that describes how fast light propagates through the material. It is defined as. where c is the speed of light in vacuum and v is the phase velocity of light in the medium. 

Answer 2

$\huge\fbox\mathcal\red{Refractive\: Index}$

Refractive index is the velocity of light in a vaccum to its velocity in a specified medium.Generally , it is a dimensionless number that describes how fast light propogates through the material.

$\huge\mathfrak\red{Thanks}$