Consider an equilateral prism (refractive index √2). A ray of light is incident on its one surface at a certain angle i. If the emergent ray is found to graze along the other surface then the angle of refraction at the incident surface is close t $o ____.$
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Question

Consider an equilateral prism (refractive index √2). A ray of light is incident on its one surface at a certain angle i. If the emergent ray is found to graze along the other surface then the angle of refraction at the incident surface is close t $o ____.$

Options

G1 Physics · Accepted Answer

For an equilateral prism, A = 60°. The emergent ray grazes the second surface, so the angle of refraction outside the prism at the second surface is e = 90°. At the second surface, Snell's law gives μ sin r₂ = 1 × sin90°. With μ = √2, √2 sin r₂ = 1. Therefore, sin r₂ = 1/√2, so r₂ = 45°. For a prism, r₁ + r₂ = A. Therefore, r₁ = 60° - 45° = 15°. Correct option: A.

Consider an equilateral prism (refractive index √2). A ray of light is incident on its one surface at a certain angle i. If the emergent ray is found to graze along the other surface then the angle of refraction at the incident surface is close t o ____.