Between point \(2\) and \(3\)
\(P_0+\rho g h^{\prime}+\frac{1}{2} \rho v^2=\sigma g h^{\prime}+P_0 \quad\left[P_0=\text { atmospheric pressure }\right]\)
\(\Rightarrow \rho g h^{\prime}+\rho g h=\sigma g h^{\prime} \quad[\because v=\sqrt{2 g h}]\)
So, \(h^{\prime}=\frac{h \rho}{\sigma-\rho}\)