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NEET Physics Wave Mechanics NEET PYQ-Wave Mechanics

  • question_answer
    The two nearest harmonics of a tube closed at one end and open at other end are 220 Hz and 260 Hz. What is the fundamental frequency of the system?                                      [NEET-2017]

    A)  40 Hz  

    B)  10 Hz

    C)  20 Hz 

    D)  30 Hz

    Correct Answer: C

    Solution :

    [c] Two successive frequencies of closed pipe
    \[\frac{nv}{4l}=220\]                 …(i)
    \[\frac{(n+2)}{4l}=260\]                        …(ii)
    Dividing (ii) by (i), we get
    \[\frac{n+2}{n}=\frac{260}{220}=\frac{13}{11}\]
    \[11n+22=13n\]
    \[n=11\]
    So,       \[11\frac{v}{4l}=220\]   \[\frac{v}{4l}=20\]
    So fundamental frequency is 20 Hz.


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