A ray of light passes from a medium with refractive index 1.60 into a medium with refractive index 1.20. If the angle of incidence is 35°, what is the angle of refraction? (Use sin 35° = 0.574 and arcsin(0.765) = 49.9°)

Correct answer

C. 49.9°

Principle or equation

Snell's law: n₁ sin θ₁ = n₂ sin θ₂.

Why this answer is correct

Here n₁ = 1.60, θ₁ = 35°, n₂ = 1.20. Then sin θ₂ = (n₁/n₂) sin θ₁ = (1.60/1.20) × 0.574 = 1.333 × 0.574 = 0.765. Therefore θ₂ = arcsin(0.765) = 49.9°.

Example

If n₁ = 1.50, θ₁ = 30°, n₂ = 1.00, then sin θ₂ = 1.50 × 0.500 = 0.750, so θ₂ = 48.6°.