A ray of light passes from air to water to glass to air. Given that the refractive index for light passing…

Analyze the question: We need the refractive index of glass relative to water, written as wn_g (light going from water into glass).

Concept: The refractive index of medium 2 relative to medium 1 is

n(1→2) = n₂ / n₁

where n₁ and n₂ are the absolute refractive indices (relative to air). So:

wn_g = an_g / an_w

Solution:

• Air to water: an_w = 4/3
• Air to glass: an_g = 3/2

wn_g = (3/2) ÷ (4/3) = (3/2) × (3/4) = 9/8 = 1.125 ≈ 1.13

Check: Glass is optically denser than water (3/2 > 4/3), so the index must be greater than 1. That rules out A, B and C, which are all below 1. (Option C, 0.75, is 3/4, which is what you'd get by wrongly using 4/3 ÷ 3/2 = 8/9 ≈ 0.89 or mixing up the fractions.)

Answer: D. 1.13.

Tip: For "index of B relative to A," always put B on top and A on the bottom: n = n_B / n_A. A quick sense check also helps: going into a denser medium gives a value greater than 1, and going into a less dense medium gives a value less than 1.