Draw a ray diagram to show two refraction of light through a glass prism. Explain with help of a diagram the dependence of angle of deviation on the angle of incidence. Hence obtain the relation for the angle of minimum deviation in terms of angle of prism and refractive index of prism.
Diagram showing refraction of light through glass prism:
Diagram showing dependence of angle of deviation on angle of incidence:
The variation of the angle of deviation with the angle of incidence is shown in the figure above. Initially it keeps decreasing with increasing incidence angle till a minimum value of deviation called the angle of minimum deviation, after which it keeps increasing again.
If the angle of the prism is A, angle of minimum deviation is dm, and refractive index is n, the relation is given by:
(Ans)