An incident ray of light strikes a diamond at an angle of 45°. The index of refraction of air is 1.0003 and the index of refraction of a diamond is 2.42.

Use Snell’s law: n₁ sin θ₁ = n₂ sin θ₂. With air as the first medium, sin θ₂ = (1.0003 × sin 45°) ÷ 2.42 ≈ 0.292, so θ₂ ≈ 17°. The refracted angle is therefore 17°, choice B.

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