What is absolute refractive index and relative refractive index?

What is the cause of refraction?

What is critical angle? How is it related with refractive index?

Define the refractive index of a medium.

What is meant by critical angle for a pair of medium? Find the relation between the cirtical angle and their refractive index.

What is refraction of light?

What is the polarising angle of a medium of refractive index sqrt3 ?