The sound of an explosion on the surface of lake is heard by a boatman 100m away and a driver 100m below the point of explosion.
(i) explain who will hear the sound of explosion first
(ii) if the sound takes t s to reach the man how much time will it take to reach the driver?
(speed of sound in air = 344 m/s
speed of sound in water = 1533 m/s )