The angle of minimum deviation of an equilateral prism is equal to its refracting angle. The refractive index of the material of the prism is:
Answer & explanation
Correct answer: option 4
The correct answer is Option (4) → 1.732
At minimum deviation the refractive index of a prism of angle \( A \) is given by the prism formula.
\( \displaystyle \mu = \frac{\sin\left(\frac{A + \delta_m}{2}\right)}{\sin\left(\frac{A}{2}\right)} \)
An equilateral prism has \( A = 60^\circ \), and here \( \delta_m = A = 60^\circ \).
\( \displaystyle \mu = \frac{\sin 60^\circ}{\sin 30^\circ} = \frac{\sqrt{3}/2}{1/2} = \sqrt{3} \approx 1.732 \)