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One train is approaching an observer at rest and another train is receding from him with the same velocity `4 m//s` . Both trains blow whistles of same frequency of `243 H_(Z)` . The beat frequency in `H_(Z)` as heard by observer is (speed of sound in air = `320 m//s`)A. 10B. 6C. 4D. 1 |
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Answer» Correct Answer - B When the train is approaching `n_1=(v)/(v-v_s)xxn=(320)/(320-4)xx243=(80)/(79)xx243` When the train is receding, `n_2=(v)/(v+v_s)xxn=(320)/(324)xx243=(80)/(81)xx243` Beat frequency is `n=n_1-n_2=80xx243((1)/(79)-(1)/(81))=6Hz` |
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