Question

What are ordinary and extra - ordinary rays?

Answer 1

The simpliest difference of Oridnary vs Extraordinary Rays in Polarisation is as under :

When light ray pass through an anisotropic medium (like calcite crystal) it splits into two rays ,

The one which obeys the laws of refraction is called The Ordinary Ray

The one which dont obey the laws of refraction is the Extraordinary Ray

Answer 2

The ray that obeys ordinary laws if reflection is called ordinary rays and which doesnt obey the ordinary laws of refraction are called extraordinary rays.