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Q.
A wire has frequency $f$. Its length is doubled by stretching. Its frequency now will be
Electromagnetic Waves
Solution:
The frequency of a wire is given by
$f=\frac{1}{T}=\frac{1}{2 \pi} \sqrt{\frac{g}{l}} $
or $ f \propto \frac{1}{\sqrt{l}} $
$\therefore \frac{f^{\prime}}{f}=\frac{\sqrt{l}}{\sqrt{l}^{\prime}} $
$\Rightarrow \frac{f^{\prime}}{f}=\frac{\sqrt{l}}{\sqrt{2 l}}=\frac{1}{\sqrt{2}}$
$\Rightarrow f^{\prime}=0.7 f\left[\because l^{\prime}=2 l\right]$