When a capillary tube is dipped in a liquid, the liquid rises to a height $h$ in the tube. The free liquid surface inside the tube is hemispherical in shape. The tube is now pushed down so that the height of the tube outside the liquid is less than $h :-$

$PQRS$ is a rectangular frame of copper wire shown in figure the side $RS$ of the frame is movable. If a soap film is formed on it then what is the diameter (in $\mathrm{mm}$ ) of the wire to maintain equilibrium (Given surface tension of soap solution $=0.045 \mathrm{N} {\mathrm{m}}^{-1}$ and density of copper $\left.=8.96\times {10}^3 \mathrm{kg} {\mathrm{m}}^{-3}\right)$

The capillary tube is dipped in water vertically. It is sufficiently long so that water rises to maximum height h in the tube. The length of the portion immersed in water is $l>h.$ The lower end of the tube is closed, the tube is taken out and opened again. Then, find the length of the water column (in metre) remaining in the tube. ( given $h=4 \mathrm{m})$