Question

Can absolute refractive index be less than 1? justify.

Answer 1

Refrative index of medium is always greater than or equal to one it can not be less than 1.

The reason is because the definition of refractive index, n of a medium (eg. glass) is the ratio of the speed of light in a vacuum, c, to the speed of light in the medium, v.
i.e. n=c/v
The minimum value of n can be 1, which is the refractive index of a vacuum or air (for which the refractive index is about the same as for a vacuum).Refractive index below 1 means a speed above the speed of light in vacuum,which is not possible in real life.so refractive index below 1 is not possible,