A ray of light is incident normally on one of the refracting surfaces of a prism of refracting angle A. The emergent ray grazes the other refracting surface. Find the refractive index of the material of the prism.

A ray of light is incident normally on one of the refracting surfaces

1.	A ray of light is incident normally on one of the refracting surfaces of a prism of refracting angle A. The emergent ray grazes the other refracting surface. Find the refractive index of the material of the prism.
Answer» SOLUTION :For normal INCIDENCE on ONE of the refracting faces of the prism `i_1=0 and r_1=0` But `r_1+r_2=A` when light undergoes refraction through a PRISMS. `therefore 0+r_2=A, r_2=A` When the emergent light grazes the second surface, `r_2` becomes the critical angle ( C) i.e., `C=A and mu=1/(sin C)=1/ (sin A)`