Physics for IGCSE & O level - Rays And Waves (Section 3 - No. 9)

What is the definition of a refractive index?

A measure of the speed of light in a medium.

The ratio of the speed of light in vacuum to the speed of light in the medium.

The amount of light bent by a lens.

The angle of incidence divided by the angle of refraction.

The refractive index is defined as the ratio of the speed of light in a vacuum to the speed of light in the medium.