InterviewSolution
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InterviewSolution
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A scooterist moves towards a vertical wall witha speed of 54 km h^(-1) . A person is standing on the ground and is behind the scooter , hears the sound . If the scooterist sounds the horn of frequency 400 Hz , calculate the apparent frequency sound heard by the person when (a) It is coming directly from the horn. (b) coming after reflection from the vertical wall. (Take speed of sound to be 330 m s^(-1)) |
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Answer» Solution :The speed of scooter = 54 km `h^(-1)` `= 54 xx 5//18= 15 m s^(-1)` The frequency of the sound of horn = 400 Hz (a) The observer with reference to the ground is at rest `implies` Velocity of observer = `0 m s^(-1)` The source of moving away from observer . `therefore` The velocity of source = `15 ms^(-1)` The apparent frequency heard by the observer is `= n^(1) = (V - V_(o))/(V + V_(s)) n = (330 - 0)/(330 + 15) xx 400` `= 0.956 xx 400 = 382 . 4` Hz (B) The apparent frequency of sound received after from the wall is `= n'' = ( 330)/(330 - 15) xx 400 = (330)/(315) xx 400 = 419` Hz [This is possible because the vertical wall reflects the sound without changing the frequency ]. |
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