Question

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 the ball as [Take _(g)=10m/s^(2).]

Answer 1

v² ball = 2×10×7.2

v = 12m/s

x image of ball = (4/3)Xball

v image of ball =(4/3)Vball = (4/3)12 = 16m/s