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Question
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`
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