question_answer 20)

                A train, standing at the outer signal of a railway station blows a whistle of frequency 400 Hz in still air. (i) What is the frequency of the whistle for a platform observer when the train (a) approaches the platform with a speed of 10 , (b) recedes from the platform with a speed of 10 ? (ii) What is the speed of sound in each case ? The speed of sound in still an- can be taken as 340 .  

Answer:

Here, v = 400 Hz, = 340 (a)    Train (source) approaches the platform,                     (b)   Train recedes from the platform,  10 m/s                           (ii) The speed of sound in each case is the same = 340 .