When light passes from one medium to another, resulting in a change in speed and direction of insolation,?

Alead ball is dropped into a lake from a diving board 5m above the water . it hits the water with a certain velocity and then sink with constant velocity in bottom . it reaches the bottom 5 second after it is dropped if g= 10m/s2 . find depth of the lake and average velocity of the ball ?

Abar magnet cut in half will form a total ofpoles.a)fourb)eightc)two

Ajoint produces movement when its angle decreases. which type of movement is it?