114 A boy is walking away from a fixed rigid wall at a speed

Last updated: 6/4/2023

114 A boy is walking away from a fixed rigid wall at a speed of 1 m s in a direction at right angles to the wall As he walks he blows a whistle steadily An observer towards whom the boy is walking hears 4 beats per second if the speed of sound is 340 m s the true frequency of the whistle is A 340 Hz B 600 Hz C 680 Hz D 500 Hz