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AFMC AFMC Solved Paper-2010

  • question_answer
    A point source emits sound equally in all directions in a non-absorbing medium. Two points P and Q are at distance of 2 m and 3 m respectively from the source. The ratio of the intensities of the waves at P and Q is

    A) 9 : 4                                       

    B) 2 : 3

    C) 3 : 2                                       

    D) 4 : 9

    Correct Answer: A

    Solution :

    Intensity \[I\propto {{(displacement)}^{2}}\] \[{{r}_{p}}=2\,m\]and \[{{r}_{Q}}=3\,m\] \[\therefore \]\[\frac{{{I}_{_{P}}}}{{{I}_{Q}}}={{\left( \frac{{{r}_{Q}}}{{{r}_{P}}} \right)}^{2}}={{\left( \frac{3}{2} \right)}^{2}}=\frac{9}{4}\]\[\Rightarrow \]  \[{{I}_{P}}:{{I}_{Q}}=9:4\]


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