JEE Main & Advanced Physics Wave Mechanics Question Bank Vibration of String

  • question_answer
    If the tension and diameter of a sonometer wire of fundamental frequency n are doubled and density is halved then its fundamental frequency will become [CBSE PMT 2001]

    A)            \[\frac{n}{4}\]                     

    B)            \[\sqrt{2}\,n\]

    C)            n    

    D)            \[\frac{n}{\sqrt{2}}\]

    Correct Answer: C

    Solution :

                         \[n=\frac{1}{2l}\sqrt{\frac{T}{\pi {{r}^{2}}\rho }}\propto \sqrt{\frac{T}{{{r}^{2}}\rho }}\]                    Þ\[\frac{{{n}_{1}}}{{{n}_{2}}}=\sqrt{\left( \frac{{{T}_{1}}}{{{T}_{2}}} \right)\,{{\left( \frac{{{r}_{2}}}{{{r}_{1}}} \right)}^{2}}\left( \frac{{{\rho }_{2}}}{{{\rho }_{1}}} \right)}=\sqrt{\left( \frac{1}{2} \right)\,{{\left( \frac{2}{1} \right)}^{2}}\left( \frac{1}{2} \right)}=1\]            \ \[{{n}_{1}}={{n}_{2}}\]


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