Question

Why angle of incidence is not equal to angle of refraction

Answer 1

Angle of Incidence is not equal to refraction because a refracted ray depends on how dense is the substance.
If a substance is dense the refracted ray will refract towards the normal that is 
                      Angle of incidence>Angle of refraction

If a substance is rare the refracted ray will refract away from the normal that is
                      Angle of incidence<Angle of refraction.

If a ray passes through any medium straight to the normal it refracts back without any deviation that is
                      Angle of incidence = 0
                      Angle of refraction = 0

Answer 2

angle of incidence is not equal to angle of refraction because as the light beem goes in an optical denser medium it comes near to the normal ray which is imaginary. also because the molecules are tightly packed that iswhy