A narrow tube of length `l` and radius `r` is sealed at one end. Its open end is brought in contact with the surface of water while the tube is held vertical. The water rises to a height `h` in the tube. The contact angle of water with the tube wall is `theta`, density of water is `rho` and the atmospheric pressure is `P_(o)`. Find the surface tension of the liquid. Assume that the temperature of air inside the tube remains constant and the volume of the meniscus is negligible.

Answer

`T=r/(2cos theta)[(P_(o)h)/(l-h)+rhogh]`