Question

Name the following.

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

Answer 1

1. The cause of refraction is the change in the speed of light as it moves from one medium to another.
2. The refraction of light in a given medium can be expressed in terms of a factor called the refractive index of the medium.
3. Refractive index of a medium is defined as the ratio of the speed of light in vacuum to the speed of light in the medium.
4. It is also called the index of refraction. It is denoted by the Greek letter $\mu$.
   $$\begin{gathered} Refractiveindex=\frac{Speedoflightinvacuum}{Speedoflightinthemedium} \\ \mu =\frac{C}{V} \end{gathered}$$.

Thus, the ratio of the speed of light in vacuum to the speed of light in a medium is called the refractive index of that medium.