Question

Explain the term absolute Refractive Index of a medium and write an expression related to it with the speed of light in vacuum

Answer 1

The refractive index of a medium is defined as the ratio of velocity of light in first medium to the velocity of light in that medium.

Mathematically refractive index  $[\eta]\ =\frac{v_{1}} { v_{2}}$

$v_{1}$  is the velocity of light in first medium.

$v_{2}$  is the velocity of light in second medium i.e the medium under consideration.

Let the first medium is space or vacuum.

Now, the velocity of light in first medium will be c where c is the velocity of light.

Now, the refractive index  $\eta\ =\frac{c}{v}$

v is the velocity of light in second medium i.e medium under consideration.

Now the refractive index obtained is called absolute refractive index.

Hence, the absolute refractive index of a medium is defined as the ratio of the velocity of light in air to the velocity of light in that medium.

Mathematically  the absolute refractive index =

                                               $\eta\ =\frac{velocity\ of\ in\ light\ air}{velocity\ of\ light\ in\ medium}$

Answer 2

Absolute refractive index is :


Velocity of light in air / Velocity of light in any medium.