When a car is approaching the observer, the frequency of horn is 100 Hz . After passing the observer, it is 50 Hz . If the observer moves with the car, the frequency will be x 3 Hz where x = _____ .

Step-by-step solution

Apparent frequency when source of moving towards observer, f 1 = 100 = f 0 c c - v s           . . . 1 Here, f 0 = frequency of observer, c = speed of sound and v s = speed of source. Apparent frequency when source of moving away from observer, f 2 = 50 = f 0 c c + v s           . . . 2 From above two equations, we have f 1 f 2 = 2 = c + v s c - v s ⇒ 2 c - 2 v s = c + v s ⇒ 3 v s = c Putting the value in equation 1 , we have 100 = f 0 c 2 c 3 = 3 2 f 0