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NEET Sample Paper NEET Sample Test Paper-11

  • question_answer
    A point source emits sound equally in all directions in a non-absorbing medium. Two points 1 and Q are at distance of 2m 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 of sound \[I=\frac{P}{4\pi {{r}^{2}}}\] or \[1\propto \frac{1}{{{r}^{2}}}\]or \[\frac{{{I}_{1}}}{{{I}_{2}}}={{\left( \frac{{{r}_{2}}}{{{r}_{1}}} \right)}^{2}}\] Here, \[{{r}_{1}}=2m,\,{{r}_{2}}=3\,m\] Substituting the values, we have\[\frac{{{I}_{2}}}{{{I}_{1}}}={{\left( \frac{3}{2} \right)}^{2}}=\frac{9}{4}\]


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