A ball is dropped from a height of 20 m above the surface of the water in a lake. The refractive index of water is 4 3 . A fish inside the lake, in the line of fall of ball is looking at the ball. At an instant, when the ball is 12 . 8 m above the water surface, the fish sees speed of ball as

Question

A ball is dropped from a height of 20 m above the surface of the water in a lake. The refractive index of water is 4 3 . A fish inside the lake, in the line of fall of ball is looking at the ball. At an instant, when the ball is 12 . 8 m above the water surface, the fish sees speed of ball as, 9 m s -1, 1 2 m s -1, 1 6 m s -1, 21.33 m s -1

MARKS App · Accepted Answer

υ = 2 gh = 2 × 1 0 × 7 = 1 2 ms -1 In this case when eye is inside water, x app. = μ x ∴ d x app. dt = μ · d x dt or, υ app. μ υ = 4 3 × 1 2 = 1 6 m s -1

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