Question

The length of the string is $216\times {10}^{-x}m.$ Find the value of x.

• A. 1
• B. 2.16
• C. 8
• D. 5

Answer 1

The correct option is B 2.16

For $n^{th}$ harmonic for string taut at two ends, $l=\frac{n\lambda }{2}$

Thus $\lambda \propto \frac{1}{n}$

Thus $\frac{n+1}{n}=\frac{0.54}{0.48}$

$⟹n=8$

$⟹l=\frac{8\times 0.54}{2}=2.16m$