Question

Why is the index of refraction a unique property of a medium?

Answer 1

The refractive index of a medium depends on the electric and magnetic properties of the medium and as a result it is very unique is dependent on the way the medium responds to electric and magnetic fields.

The velocity of light in a medium,

`v = 1/sqrt(muepsilon)` where `mu` and `epsilon` are the magnetic permeability and electric permittivity of the medium respectively.

Also, velocity of light in vacuum,

`c = 1/sqrt(mu_0epsilon_0)` where `epsilon_0` and `mu_0` are the permittivity and permeability of free space respectively.

Therefore, the refractive index,

`n = c/v = sqrt ((epsilonmu)/(epsilon_0mu_0))`

But, `epsilon_0` and `mu_0` are fundamental constants and hence `n` depends on electric and magnetic properties `epsilon` and `mu` of the medium which are unique of the medium.