Three liquids of densities $\rho_1, \rho_2$ and $\rho_3$ (with $\rho_1\gt\rho_2\gt\rho_3$ ) having same…
Three liquids of densities $\rho_1, \rho_2$ and $\rho_3$ (with $\rho_1\gt\rho_2\gt\rho_3$ ) having same value of surface tension T , rise to the same height in three identical capillaries. Angle of contact $\theta_1, \theta_2$ and $\theta_3$ respectively obey
Rise of a liquid in a capillary tube:
$\begin{aligned}
& \mathrm{h}=\frac{2 \mathrm{~T} \cos \theta}{\mathrm{rg} \rho} \\
& \cos \theta=\frac{\mathrm{hr} \rho \mathrm{~g}}{2 \mathrm{~T}}
\end{aligned}$
$\ldots .(\because \cos 0=1$ is the max. value for cosine $)$
$\therefore \quad$ Here, $\rho_1\gt\rho_2\gt\rho_3$, so
$\theta_1 \lt \theta_2 \lt \theta_3$ The all three angles of contact should be acute.
$0 \leqslant \theta_1 \lt \theta_2 \lt \theta_3 \lt \frac{\pi}{2}$