we have
sini=μsinA
i≈μA
as it emerges normally from the figure you will get the angle of refraction after fiurst surface = A
A ray is incident at an angle of incidence i on one surface of a prism of small angle A and emerges normally from opposite surface. If the refractive index of the material of prism is μ, the angle incidence of i is nearly equal to
we have
sini=μsinA
i≈μA
as it emerges normally from the figure you will get the angle of refraction after fiurst surface = A