Question

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.

Hint:

For a prism, the condition of minimum deviation is special because it's symmetric: angle of incidence (\(i\)) equals the angle of emergence (\(e\)). Visually, this is when the light ray inside the prism is parallel to the prism's base.

Answer 1

Step 1: Understanding the Concept:
The path of light through a prism depends on the angle of incidence (\( i \)). For an isosceles prism, when the refracted ray is parallel to the base, the prism is in the state of minimum deviation (\( \delta_m \)).
Step 2: Detailed Explanation:
- (c) \( i = e \): Diagram C shows the refracted ray passing through the prism parallel to its base. This is the specific condition for minimum deviation where the angle of incidence equals the angle of emergence (\( i = e \)).
- (b) Minimum incidence: Diagram B shows the incident ray entering almost normally to the surface (the angle with the normal is very small). Thus, this corresponds to the minimum angle of incidence among the choices.
- (a) Maximum incidence: Diagram A shows the ray striking the first surface at a very steep angle (grazing incidence or large angle with the normal), resulting in the most significant bending toward the base.
Step 3: Final Answer:
(a) Diagram A, (b) Diagram B, (c) Diagram C.