Light travels from air (n = 1.00) into water (n = 1.33) at an incident angle of 30° from the normal. What is the approximate refracted angle in water?
A22°
B30°
C42°
D48°
Applying Snell's law: n₁ sinθ₁ = n₂ sinθ₂ → (1.00)(sin 30°) = (1.33)(sin θ₂) → sin θ₂ = 0.5/1.33 ≈ 0.376 → θ₂ ≈ 22°. Because light enters a denser medium (higher n), it bends toward the normal, so the refracted angle is smaller than the incident angle.
Question 2 True / False
When light passes from air into glass (higher index of refraction), it bends away from the normal.
TTrue
FFalse
Answer: False
Light bends toward the normal when entering a medium with a higher index of refraction. A higher index means a slower wave speed. Because the frequency is fixed (it doesn't change at the boundary), the wavelength shortens, and the wavefront pivots toward the normal. Bending away from the normal happens only when going from a higher-index medium back to a lower-index one.
Question 3 Short Answer
Why does the index of refraction determine how much light bends at a boundary, and what does a higher index tell you about light's speed in that medium?
Think about your answer, then reveal below.
Model answer: The index of refraction n = c/v, so a higher n means light travels more slowly in that medium. At a boundary, frequency is preserved but speed changes, forcing the wavelength and direction to change. The greater the speed difference (larger Δn), the more the ray bends.
Snell's law is fundamentally a consequence of wave physics: the component of the wave's phase velocity parallel to the boundary must be continuous across it. This forces n₁ sinθ₁ = n₂ sinθ₂. A medium with a high refractive index slows light dramatically, causing a large bend for even moderate incident angles.