A thin uniform tube is bent into a circle of radius r in the vertical plane. Equal volumes of two immiscible liquids, whose densities are ρ_1 and…

A thin uniform tube is bent into a circle of radius r in the vertical plane. Equal volumes of two immiscible liquids, whose densities are $\displaystyle \rho_1$ and $\displaystyle \rho_2\left(\rho_1>\rho_2\right)$, fill half the circle. The angle $\displaystyle \theta$ between the radius vector passing through the common interface and the vertical is :