An equilateral prism has prism angle A = 60°. Its angle of minimum deviation is equal to half the prism angle. What is the refractive index of the prism?
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Question

An equilateral prism has prism angle A = 60°. Its angle of minimum deviation is equal to half the prism angle. What is the refractive index of the prism?

G1 Physics · Accepted Answer

For a prism at minimum deviation, μ = sin[(A+δ(min)) ÷ 2] ÷ sin(A ÷ 2). For an equilateral prism, A = 60°. Given, δ(min) = A ÷ 2 = 30°. Therefore, μ = sin45° ÷ sin30° = (1 ÷ √2) ÷ (1 ÷ 2) = √2. Correct option: C.