Now, as crest spread, this energy $E$ remains constant. So,
$2 \pi r d r h^{2} \rho g=E$
$\Rightarrow \mathrm{h}=\sqrt{\frac{\mathrm{E}}{2 \pi \mathrm{rdr} \rho \mathrm{g}}}$ or $\mathrm{h} \propto \mathrm{r}^{-1 / 2}$


$(A)$ With a node at $O$, the minimum frequency of vibration of the composite string is $v_0$
$(B)$ With an antinode at $O$, the minimum frequency of vibration of the composite string is $2 v_0$
$(C)$ When the composite string vibrates at the minimum frequency with a node at $O$, it has $6$ nodes, including the end nodes
$(D)$ No vibrational mode with an antinode at $O$ is possible for the composite string