Question

Question #eb96f

Answer 1

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

Explanation:

The refractive index of a material is defined as the ratio of the speed of light in vacuum to the speed of light in the material:

`n = c/v`

Where `n` is the index of refaction, `v` is the speed of light in the material and `c = 2.99792xx10^8m//s` is the speed of light in vacuum.

The speed of light in a material is always less than the speed of light in vacuum, so the ratio is always a number greater than `1`.

Unless we are talking about vacuum itself, where the speed of light is that of the vacuum, such that the refractive index of free-space is `1`. This is a necessary concept for calculations requiring the refractive index on two sides of a boundary, where one is free space and the other is a material of some kind.