Discuss refraction from denser to rerer medium at a convex spherical refracting surface.

Discuss briefly refraction from rarer to denser medium at a concave spherical refracting surface.

Prove that (-mu_1)/(u)+(mu_2)/(v) = (mu_2 - mu_1)/( R) when refraction occurs from rarer to denser medium at a concave spherical refracting surface.

The relation governing refraction of light from rarer to denser medium at a spherical refracting surface is

Define pole of a spherical refracting surface.