Q104 / 125 · BITSAT 2014 · Physics

When a string is divided into three segments of length $l_{1}, l_{2},$ and $l_{3}$, the fundamental frequencies of these three segments are $v_{1}, v_{2}$ and $v_{3}$ respectively. The original fundamental frequency (v) of the string is

  • A
    $\quad \sqrt{v}=\sqrt{v_{1}}+\sqrt{v_{2}}+\sqrt{v_{3}}$
  • B
    $v=v_{1}+v_{2}+v_{3}$
  • Correct answer
    C
    $\frac{1}{v}=\frac{1}{v_{1}}+\frac{1}{v_{2}}+\frac{1}{v_{3}}$.
  • D
    $\frac{1}{\sqrt{v}}=\frac{1}{\sqrt{v_{1}}}+\frac{1}{\sqrt{v_{2}}}+\frac{1}{\sqrt{v_{3}}}$

Solution

Fundamental frequency is given by $$ v=\frac{1}{2 l} \sqrt{\frac{T}{\mu}} \Rightarrow v \propto \frac{1}{l} \Rightarrow P \propto \frac{1}{v} $$ Since, $P$ divided into $l_{1}, l_{2}$ and $l_{3}$ segments Here $l=l_{1}+l_{2}+l_{3}$ So $\quad \frac{1}{v}=\frac{1}{v_{1}}+\frac{1}{v_{2}}+\frac{1}{v_{3}}$

Hence, the correct answer is option: 'C'.

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