Question

A ray of light passes through a triangular prism. Show graphically how the angle of deviation varies with the angle of incidence. Hence define the angle of minimum deviation

Hint:

Prism Deviation and Refractive Index

Answer 1

The angle of deviation (δ) of light passing through a prism varies with the angle of incidence (i) as shown below. The angle of deviation initially decreases, reaches a minimum value, and then increases as the angle of incidence increases

Definition of Minimum Deviation (δm):
The angle of minimum deviation (δm) is the smallest angle of deviation that occurs when the light passes symmetrically through the prism, i.e., when the angle of incidence equals the angle of emergence.