Question

What is refractive index? What is the meaning of refractive index of water?

Answer 1

Refractive index is the ratio of speed of light on air to the speed of light on given medium.

Refractive index of water means the ratio of speed of light in air to the speed of light in vacuum.

Answer 2

Explanation:

For example, the refractive index of water is 1.333, meaning that light travels 1.333 times as fast in vacuum as in water. Increasing refractive index corresponds to decreasing speed of light in the material.