Answer:
Option B
Explanation:
According to question , energy in string per unit volume is given by $\frac{1}{2}$ x stress x strain
$\frac{U}{V}=\frac{1}{2}\times\frac{F}{A}\times\frac{\triangle l}{l}$
[ Symbols have their usual meanings]
= $\frac{1}{2} \times V \times (strain)^{2}$
$\frac{U_{s}}{S_{L}}=\frac{Y_{s}}{Y_{L}}\times\left(\frac{stress(S)}{Strain(L)}\right)^{2}$
= $\frac{A_{L}}{A_{s}}=\left(\frac{l}{l}\right)^{2}$
$\Rightarrow$ $\frac{r_{L}^{2}}{r_{s}^{2}}=\frac{3^2}{l^{2}}=9:1$
