Physics - Wave on String Question with Solution | TestHub

At resonance $f=\frac{n}{2l}\sqrt{T_1/\mu }$ and $f=\frac{n+1}{2l}\sqrt{T_2/\mu }$ with $T_1>T_2$. The larger tension has the smaller $n$: $n=2lf\sqrt{\mu /T_1}$, $n+1=2lf\sqrt{\mu /T_2}$. Subtracting: $1=2lf\sqrt{\mu }\left(\frac{1}{\sqrt{T_2}}-\frac{1}{\sqrt{T_1}}\right)=2lf\sqrt{\mu }\frac{\sqrt{T_1}-\sqrt{T_2}}{\sqrt{T_1{T}_2}}$. So $\mu =\frac{T_1{T}_2}{4f^2{l}^2{(\sqrt{T_1}-\sqrt{T_2})}^2}$, which matches none of A, B, C. Printed key D agrees.