The angle of incidence for an equilateral prism having an angle of minimum deviation of 30° will be:
Answer & explanation
Correct answer: option 3
The correct answer is Option (3) → \( 45^\circ \)
For a prism of angle A, the deviation is \( \delta = i + e - A \). At minimum deviation the ray passes symmetrically, so the angle of incidence equals the angle of emergence, \( i = e \).
\( \delta_m = 2i - A \Rightarrow i = \frac{A + \delta_m}{2} \)
An equilateral prism has \( A = 60^\circ \).
\( i = \frac{60^\circ + 30^\circ}{2} = 45^\circ \)