A ray of light is incident on an equilateral prism at an angle of \( 45^\circ \) and is refracted parallel to the base of the prism. The angle of deviation would be
Answer & explanation
Correct answer: option 2
The correct answer is Option (2) → \( 30^\circ \)
For an equilateral prism the angle of the prism is \( A = 60^\circ \). A ray refracted parallel to the base passes symmetrically through the prism, so the angle of emergence equals the angle of incidence:
\( \displaystyle e = i = 45^\circ \)
The angle of deviation is
\( \displaystyle \delta = i + e - A = 45^\circ + 45^\circ - 60^\circ = 30^\circ \)
This is also the minimum deviation, since the passage is symmetric.