JEE Main · 2026 · 02 Apr 2026 · Shift 1 · Geometrical Optics

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For a thin symmetric prism made of glass (refractive index 1.5), the ratio of incident angle and minimum deviation will be ____.

(A) $3 : 4$
(B) $3 : 2$ ✓ Correct
(C) $2 : 1$
(D) $1 : 2$

Answer: (B)

Solution

For a thin prism the minimum deviation is

δ_{m} = (μ - 1) A = (0.5) A = \frac{A}{2}

. At minimum deviation the ray passes symmetrically, so the angle of incidence is

i = \frac{A + δ _{m}}{2} = \frac{A + A /2}{2} = \frac{3 A}{4}

. Hence

\frac{i}{δ _{m}} = \frac{3 A /4}{A /2} = \frac{3}{2}

. The ratio of the incident angle to the minimum deviation is

3 : 2

JEE Main · 2026 · 02 Apr 2026 · Shift 1 · Single correct option

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