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

  • question_answer
    Three similar wires of frequency n1, n2 and n3 are joined to make one wire. Its frequency will be                                                                                        [CBSE PMT 2000]

    A)                                                      \[n={{n}_{1}}+{{n}_{2}}+{{n}_{3}}\]                               

    B)            \[\frac{1}{n}=\frac{1}{{{n}_{1}}}+\frac{1}{{{n}_{2}}}+\frac{1}{{{n}_{3}}}\]

    C)            \[\frac{1}{\sqrt{n}}=\frac{1}{\sqrt{{{n}_{1}}}}+\frac{1}{\sqrt{{{n}_{2}}}}+\frac{1}{\sqrt{{{n}_{3}}}}\]             

    D)            \[\frac{1}{{{n}^{1}}}=\frac{1}{n_{1}^{2}}+\frac{1}{n_{2}^{2}}+\frac{1}{n_{3}^{2}}\]

    Correct Answer: B

    Solution :

                         \[n=\frac{1}{2l}\sqrt{\frac{T}{m}}\]Þ \[{{n}_{1}}{{l}_{1}}={{n}_{2}}{{l}_{2}}={{n}_{3}}{{l}_{3}}=k\]                    \[{{l}_{1}}+{{l}_{2}}+{{l}_{3}}=l\]Þ\[\frac{k}{{{n}_{1}}}+\frac{k}{{{n}_{2}}}+\frac{k}{{{n}_{3}}}=\frac{k}{n}\]            Þ \[\frac{1}{n}=\frac{1}{{{n}_{1}}}+\frac{1}{{{n}_{2}}}+\frac{1}{{{n}_{3}}}+........\]


You need to login to perform this action.
You will be redirected in 3 sec spinner