JEE Main · 2026 · 06 Apr 2026 · Shift 2 · Geometrical Optics

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Angle of minimum deviation is equal to the half of the angle of prism in an equilateral prism. The refractive index of the prism is ______.

(A)1.5
(B) $3$
(C) $2$ ✓ Correct
(D)1.65

Answer: (C)

Solution

For an equilateral prism

A = 6 0^{\circ}

, and here

δ_{m} = \frac{A}{2} = 3 0^{\circ}

. The refractive index is

μ = \frac{sin \frac{A + δ _{m}}{2}}{sin \frac{A}{2}} = \frac{sin 4 5 ^{\circ}}{sin 3 0 ^{\circ}} = \frac{1/ 2}{1/2} = 2

JEE Main · 2026 · 06 Apr 2026 · Shift 2 · Single correct option

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