The angle of refraction is found to be half the angle of refraction. Then refractive index of medium is

A ray of light passes from vaccuum to a medium refractive index mu . The angle of incidence is found to be twice the angle of refraction. The angle of refraction is

The relation between angle of the prism and refractive index of the medium is:

How is the critical angle related to the refractive index of a medium ?