What is the critical angle for total internal reflection at a boundary between glass (refractive index n1 = 1.50) and water (n2 = 1.33)?
Answer and explanation
Correct answer: A. 62.5 degrees
- Step 1: Snell's law at critical angle: sin(theta_c) = n2 / n1. Step 2. sin(theta_c) = 1.333 / 1.500 = 8/9 = 0.8889. Step 3. theta_c = arcsin(0.8889) = 62.73° approx. 62.5°. Answer: 62.5 degrees. Why not the others: 41.8° is glass to air (1/1.5); 48.8° is water to air (1/1.33).
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