A ray of monochromatic light passes through an equilateral prism ABC. The refracted ray inside the prism (QR) travels parallel to the base BC, and the angle of incidence is 50°. Find the deviation δ. Image
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Question

A ray of monochromatic light passes through an equilateral prism ABC. The refracted ray inside the prism (QR) travels parallel to the base BC, and the angle of incidence is 50°. Find the deviation δ. Image

Options

G1 Physics · Accepted Answer

Step 1: For an equilateral prism, apex angle A = 60°. Step 2: A ray parallel to the base inside a symmetric equilateral prism has equal refraction angles: r₁ = r₂ = A/2 = 30°. Step 3: The ray path is symmetric, giving emergence angle e = incidence angle i = 50°. Step 4: Prism deviation: δ = i + e − A = 50° + 50° − 60° = 40°. Final answer: δ = 40° (Option D).