A thin prism has different medium on its either side. A light ray is incident almost normally on the first face. What is the angle of deviation if all the angles are very small

Question

A thin prism has different medium on its either side. A light ray is incident almost normally on the first face. What is the angle of deviation if all the angles are very small, I 1 - μ 1 μ 2 - A 1 - μ μ 2, I 1 - μ 1 μ 2 + A 1 - μ μ 2, I 1 + μ 1 μ 2 - A 1 - μ μ 2, none of these

MARKS App · Accepted Answer

From Snell's law at first refraction, μ 1 I = μ r 1 r 1 = I μ 1 μ ...(1) From Snell's law at second refraction, μ r 2 = μ 2 e μ A - r 1 = μ 2 e ∴ From (1), μ A - I μ 1 μ = μ 2 e e = μ μ 2 A - I μ 1 μ ...(2) Overall deviation, δ = I + e - A δ = I + μ μ 2 A - I μ 1 μ - A δ = I 1 - μ 1 μ 2 - A 1 - μ μ 2

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