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. When the ball is 12.8 m above the water surface, what speed does the fish see the ball as? Take g=10 m/s2.
a. 9 m/s
b. 12 m/s
c. 16 m/s
d. 21.33 m/s