# A train blows a whistle of frequency 640 Hz in air. Find the difference in apparent frequencies of the whistle for a stationary observer, when the train moves towards and away from the - Physics

Numerical

A train blows a whistle of frequency 640 Hz in air. Find the difference in apparent frequencies of the whistle for a stationary observer, when the train moves towards and away from the observer with the speed of 72 Km/hour. [Speed of sound in air = 340 m/s.]

#### Solution

N_1=N(V/(V-V_s))

V_s=72

N_1=640(340/(340-20))

N_1=680 Hz

N_2=N(V/(V+v_s))

V_s=72

N_2=640(340/(340+20))

N_2=604.4 Hz

Concept: Formation of Beats
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