A light ray travels from a transparent medium with refractive index 1.60 into another transparent medium with refractive index 1.20. If the angle of incidence is 30°, what is the angle of refraction? (Use sin 30° = 0.500 and arcsin(0.667) = 41.8°)
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Correct answer
C. 41.8°
Principle or equation
Snell's law: n1 sin θ1 = n2 sin θ2, where n is refractive index and θ is the angle with the normal.
Why this answer is correct
Given n1 = 1.60, θ1 = 30°, n2 = 1.20. Solve for θ2: sin θ2 = (n1/n2) sin θ1 = (1.60/1.20) × 0.500 = 0.667. Thus θ2 = arcsin(0.667) = 41.8°.
Example
If light goes from glass (n=1.5) to air (n=1.0) at 30°, sin θ2 = (1.5/1.0) sin 30° = 0.75, so θ2 ≈ 48.6°.
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