Discuss the refraction of light through a prism. What are angle of deviation and angle of emergence? How are these angles related to the angle of incidence and the angle of prism?

Refraction through a glass prism: Fig. shows the principal section ABC of a glass prism. A ray PQ is incident on face AS. As it enters the denser medium (glass), it bends away from the normal along path QR. The ray QR again suffers refraction at face AC; benging away from the normal, it emerges along RS. The angle D between the incident ray and the emergent ray is called the angle of deviation. The angle e made by the emergent ray with the normal to the refracting face AC is called the angle of emergence.

Clearly, a light bends towards the base of the prism as it suffers refraction through the prism. It is seen that ray
i + e = A + D
In other words,
Angle of incidence + Angle of emergence = Angle of prism + Angle of deviation