IIT-JEE Exam

A ball is dropped from a height of 20 m above the surface of water in a lake. The refractive index of water
is 4/3. A fish inside the lake, in the line of fall of the ball, is looking at the ball. At an instant, when the ball
is 12.8 m above the water surface, the fish sees the speed of ball as
(A) 9 m/s (B) 12 m/s
(C) 16 m/s (D) 21.33 m/s

Read Solution (Total 1)

The overall thing is the fish will perceive the ball to fall from a shorter height. So its speed at any time will also appear slower.
Its true V after (20 - 12.8) = 7.2m. will be sqrt. (2gh) = 12m/sec.
(12/4) x 3 = 9m/sec. observed by the fish.
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IIT-JEE Other Question

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