Question

What is refractive index ?

Answer 1

In optics, the refractive index or index of refraction of a material is a dimensionless number that describes how light propagates through that medium. It is defined as

n=c/v

where c is the speed of light in vacuum and vis the phase velocity of light in the medium. For example, the refractive index of water is 1.333, meaning that light travels 1.333 times slower in water than in the vacuum.