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JEE Main & Advanced Physics Wave Mechanics Question Bank Doppler's Effect

  • question_answer
    A small source of sound moves on a circle as shown in the figure and an observer is standing on \[O\]. Let \[{{n}_{1}},\ {{n}_{2}}\] and \[{{n}_{3}}\]be the frequencies heard when the source is at \[A,\ B\] and \[C\] respectively. Then                    [UPSEAT 2002]

    A)            \[{{n}_{1}}>{{n}_{2}}>{{n}_{3}}\]

    B)            \[{{n}_{2}}>{{n}_{3}}>{{n}_{1}}\]

    C)            \[{{n}_{1}}={{n}_{2}}>{{n}_{3}}\]

    D)            \[{{n}_{2}}>{{n}_{1}}>{{n}_{3}}\]

    Correct Answer: B

    Solution :

               At point A, source is moving away from observer so apparent frequency \[{{n}_{1}}<n\] (actual frequency) At point B source is coming towards observer so apparent frequency \[{{n}_{2}}>n\] and point C source is moving perpendicular to observer so \[{{n}_{3}}=n\] Hence \[{{n}_{2}}>{{n}_{3}}>{{n}_{1}}\]


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