A man is standing on the platform and one train is approaching and another train is going away with the speed of 4 m s - 1 , frequency of sound produced by train is 240 Hz . What will be the number of beats heard by him per second? (velocity of sound = 300 m s - 1 )

Step-by-step solution

The apparent frequency heard by the man is given by n a p p = n v ± v o v ± v s On our case, v o = 0 ∴ n a p p = n v v ± v s Given, v = 300   m   s - 1 ,   v s = 4   m   s - 1 ,   n = 240   H z In the first case, the train is approaching the man, so frequency heard n 1 = n v v ± v s = 240 300 300 - 4 = 240 × 300 296 = 243.24   H z In the second case, the train is going away from the man, so frequency heard n 2 = n v v + v s = 240   300 300