Define refractive index?

What is the significance of refractive index?

Define Snell's law. What is refractive index? Write its mathematical formula.

What is the unit of refractive index?

What happens when a convex lens of refractive index 1.2 is immersed in a liquid of refractive index 1.3?

A glass of refractive index 1.45 disappears when immersed in a liquid. What is the value of refractive index of the light?

How polarising angle is related to refractive index?

Derive a relation between refractive index and critical angle.

A glass lens of refractive index 1.5 is placed in a trough of liquid. What must to be the refractive index of the liquid in order to make the lens diappear.