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Question:

A diver looking up through the water sees the outside world contained in a circular horizon. The refractive index of water is 4/3, and the diver's eyes are 15 cm below the surface of water. Then the radius of the circle is :

15×3√7cm

15×√73cm

15×3×√5cm

15×3√7cm

Solution:

sin(θc) = 1/μ = 3/4 = R/√15² + R²
By solving this above equation, we get
R = 15×3√7cm