QQuestion
A monochromatic ray strikes the surface of identical prisms (A, B and C) at different angles of incidence. The diagram below shows their refracted rays. Study the path of these refracted rays and identify in which of the diagrams:
(a) the angle of incidence is maximum.
(b) the angle of incidence is minimum.
(c) the angle of incidence is equal to the angle of emergence.
✓Answer
(a) The angle of incidence is maximum for prism B.
(b) The angle of incidence is minimum for prism A.
(c) The angle of incidence is equal to the angle of emergence for prism C.
Explanation:
For identical prisms, a larger angle of incidence produces a refracted ray inside the prism making a larger angle with the normal. Hence, diagram B corresponds to maximum incidence, while diagram A corresponds to minimum incidence.
When the angle of incidence is equal to the angle of emergence, the path of the ray through the prism is symmetrical, and the refracted ray inside the prism becomes parallel to the base. This is shown in diagram C.
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