Critical angle for total internal reflection from water (n = 4/3) to air:
Asin⁻¹(3/4)
Bsin⁻¹(4/3)
C30 degrees
D60 degrees
Answer & Solution
Correct answer: A. sin⁻¹(3/4)
At critical angle, sin(c)/sin(90) = 1/n, so sin(c) = 1/n = 3/4. c = sin⁻¹(3/4) ≈ 48.6 degrees. Beyond this angle, light is totally reflected back into water.
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