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

  • question_answer
    Fundamental frequency of sonometer wire is n. If the length, tension and diameter of wire are tripled, the new fundamental frequency is                                         [DPMT 2002]

    A)            \[\frac{n}{\sqrt{3}}\]        

    B)            \[\frac{n}{3}\]

    C)            \[n\sqrt{3}\]                        

    D)            \[\frac{n}{3\sqrt{3}}\]

    Correct Answer: D

    Solution :

                         \[n=\frac{1}{2l}\sqrt{\frac{T}{\pi {{r}^{2}}\rho }}\Rightarrow n\propto \frac{\sqrt{T}}{lr}\] Þ \[\frac{{{n}_{1}}}{{{n}_{2}}}=\sqrt{\frac{{{T}_{1}}}{{{T}_{2}}}}\times \frac{{{l}_{2}}}{{{l}_{1}}}\times \frac{{{r}_{2}}}{{{r}_{1}}}\]            \[=\sqrt{\frac{T}{3T}}\times \frac{3l}{l}\times \frac{2r}{r}=3\sqrt{3}\]Þ \[{{n}_{2}}=\frac{n}{3\sqrt{3}}\]


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