Light passes from air (n = 1.0) into glass (n = 1.5) with an angle of incidence of 30°. What is the angle of refraction? (sin 30° = 0.5, sin 19.5° ≈ 0.333)
Show the answer and explanation
Correct answer
A. 19.5°
Principle or equation
Snell's law: n1 sin θ1 = n2 sin θ2.
Why this answer is correct
1.0 × sin 30° = 1.5 × sin θ2 → sin θ2 = 0.5 / 1.5 = 0.333 → θ2 ≈ 19.5°.
Example
From water (n=1.33) to air (n=1), if θ1=30°, then sin θ2 = 1.33×0.5 = 0.665, θ2≈41.7°.
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