JCECE Engineering JCECE Engineering Solved Paper-2007

  • question_answer
    A closed organ pipe of length 20 cm is sounded with tuning fork in resonance. What is the frequency of tuning fork?\[(v=332\,\,m/s)\]

    A) \[300\,\,Hz\]                     

    B) \[350\,\,Hz\]

    C) \[375\,\,Hz\]                     

    D)  \[415\,\,Hz\]

    Correct Answer: D

    Solution :

    Key Idea: When length of air column is\[\frac{\lambda }{4}\], then first resonance occurs. If we adjust the length of air-column in closed organ pipe as such its any natural frequency equals to the frequency of tuning fork, then the amplitude of forced vibrations of air-column increases very much. This is the state of resonance. At first resonance                 \[l=\frac{\lambda }{4}\] So, frequency of tuning fork                 \[f=\frac{v}{\lambda }=\frac{v}{4l}\] Given,\[l=20\,\,cm=0.2\,\,m,\,\,v=332\,\,m/s\] Hence,\[f=\frac{332}{4\times 0.2}=415\,\,Hz\]


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