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9th Class Science Sound Question Bank Sound

  • question_answer
    A tuning fork of unknown frequency when sounded ' with   another   of   256   Hz   gives 4 beats/sec. When a loaded with a certain amount of wax it is found give 2 beats. The unknown frequency is

    A)  240 Hz          

    B)         250 Hz

    C)  260 Hz                   

    D)         270 Hz

    Correct Answer: C

    Solution :

     Unknown frequency\[=256\pm 4\,\,Hz\]                 \[=260\,\,Hz\,\,or\,\,252\,\,Hz\] When \[A\] is loaded with wax, its frequency decreases, i.e. the number of beats is decreased \[\therefore \]Unknown frequency\[=260\,\,Hz\].


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