Question

What is critical angle and relation between refractive Index and Critical Angle ?

Answer 1

May be it helps you :-the angle of incidence beyond which rays of light passing through a denser medium to the surface of a less dense medium are no longer refracted but totally reflected called critical angle.
velocity with the definition of index ofrefraction, we find a relationship between the wavelength = v/f in a medium and the wavelength 0 = c/f in vacuum: In the above equation, the frequencies cancel because frequency does not change as light moves from one medium to another.

Answer 2

critical angle is the angle above which if we incident a light ray in a medium it totally reflect.
and relation is refractive index= sin critical angle or u = sin i.