Question

A light ray passes from air (\( \mu = 1 \)) into a glass slab (\( \mu = 1.5 \)) at an angle of incidence of \( 30^\circ \). What is the angle of refraction inside the glass slab?

• A. \( 19.5^\circ \)
• B. \( 22.5^\circ \)
• C. \( 35.0^\circ \)
• D. \( 45.0^\circ

Hint:

\textbf{Key Fact:} When light enters a denser medium, the angle of refraction is smaller than the angle of incidence due to bending toward the normal.

Answer 1

The Correct Option is A

• Snell's Law: μ₁ sin θ₁ = μ₂ sin θ₂, where μ₁ = 1 (air), μ₂ = 1.5 (glass), θ₁ = 30°, and θ₂ is the angle of refraction.
• Compute sin 30°: sin 30° = 0.5.
• Apply Snell’s Law: 1 × sin 30° = 1.5 × sin θ₂, so 0.5 = 1.5 sin θ₂, thus sin θ₂ = 0.5 / 1.5 = 1/3 ≈ 0.333.
• Find θ₂: θ₂ = sin^-1(0.333). Using approximate values, sin^-1(0.333) ≈ 19.47°, which rounds to 19.5°.
• Conclusion: The angle of refraction is (1) 19.5°.