Question

Write a variable and dimensionless physical quantity

Answer 1

Refractive index of the material is given by:

$$\begin{gathered} \mu =\frac{velocityoflightinvacuum}{velocityoflightinmedium} \\ \mu =\frac{c}{v} \end{gathered}$$

Hence refractive index is the dimensional less quantity which is different for different mediums.