Question

The sound of an explosion on the surface of a lake is heard by a boat man 100 m away and by a diver 100 m below the point of explosion.

(i) Who would hear the sound first: boatman or diver?

(ii) Give a reason for your answer in part (i).

(iii) If sound takes time t to reach the boatman, how much time approximately does it take to reach the diver? 

Answer 1

(i) The diver would hear the sound first.

(ii) Because the velocity of sound in water (1450 ms^-1) is more than the velocity of sound in air (332 ms^-1).

(iii) Time taken by sound to reach the diver would be less than t, where t is the time taken by sound to reach the boatman.

Note: Time taken by sound to reach the diver would be 4.36 times less than the time taken by sound to reach the boatman.