When a ray of light is incident at an angle of incidence 60° on one face of an equilateral prism the angle of deviation is found to be minimum. The refractive index of the prism material is:
Answer & explanation
Correct answer: option 1
The correct answer is Option (1) → \( \sqrt{3} \)
At minimum deviation the ray passes through the prism symmetrically, so the angles of refraction at the two faces are equal and each is half the angle of the prism.
\( A = 60^\circ \text{ (equilateral prism)} \)
\( r = A/2 = 30^\circ \)
By Snell's law at the first face,
\( \displaystyle \mu = \frac{\sin i}{\sin r} = \frac{\sin 60^\circ}{\sin 30^\circ} = \frac{\sqrt{3}/2}{1/2} = \sqrt{3} \)
Note: The same question was also asked in CUET (UG) 2026 on 19-05-2026 (Slot 1).