RAJASTHAN PMT Rajasthan - PMT Solved Paper-2003

  • question_answer
    Two vibrating tuning forks produce waves given by \[{{y}_{1}}=4\sin \,500\pi t,\] \[{{y}_{1}}=2\sin \,506\pi t\] If they are held near the ear of a person, the person will hear

    A)  3 beats/second with intensity ratio of maxima to minima equal to 9

    B)  3 beats/second with intensity ratio of maxima to minima equal to 2

    C)  6 beats/second with intensity ratio of maxima to minima to equal to 2

    D)  6 beats/second with intensity ratio of maxima to minima equal to 9

    Correct Answer: A

    Solution :

    Comparing given equation with standard equations \[y=A\,\sin \,\omega t\]             We get    \[{{A}_{1}}=4,\,\,{{\omega }_{1}}=500\,\pi \]             and          \[{{A}_{2}}=2,{{\omega }_{2}}=506\pi \]             Frequency \[n=\frac{\omega }{2\pi }\]             \[\therefore \]      \[{{n}_{1}}=\frac{{{\omega }_{1}}}{2\pi }=\frac{500\pi }{2\pi }=250\]                                 \[{{n}_{2}}=\frac{{{\omega }_{2}}}{2\pi }=\frac{506\pi }{2\pi }=253\]             Number of beats                                 \[={{n}_{2}}-{{n}_{1}}=253-250=3\]                 \[\frac{{{I}_{\max }}}{{{\operatorname{I}}_{\min }}}=\frac{{{({{A}_{1}}+{{A}_{2}})}^{_{2}}}}{({{A}_{1}}-{{A}_{2}})}\]                 \[=\frac{{{(A+2)}^{_{2}}}}{{{(A-2)}^{2}}}={{\left( \frac{6}{2} \right)}^{2}}=\frac{9}{1}\]


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