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NEET Sample Paper NEET Sample Test Paper-46

  • question_answer
    Two whistles A and B produce notes of frequencies 660 Hz and 596 Hz, respectively. There is a listener at the midpoint of the line joining them. Both the whistle B and the listener start moving with speed 30 m/s away from whistle A. If the speed of sound is 330 m/s, how many beats will be heard by the listener?

    A) 2

    B)                    4

    C)                    6

    D)                    8

    Correct Answer: B

    Solution :

    Here, whistle B and listener (both) are moving with same speed. Hence, there will be no change in the pitch of whistle B to the listener. Frequency of the note from A will be: \[n'=n\left( \frac{v-{{v}_{0}}}{v} \right)\,\,=\,\,600\,\left( \frac{330-30}{330} \right)\,\,=\,\,600\,\,Hz\] \[\therefore \,\,\,Beat\,\,frequency=\text{ }600-596=4\text{ }Hz.\]


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