The excess pressure inside a soap bubble of radius 6mm is balanced by 2mm column of oil of specific gravity .8. find the surface tension of the soap solution.

dP = 4T /r

The pressure to height column of oil

P = hρg

Since the excess pressure inside the bubble is balance by the height of the column:

4T/r = hρg

or, T = rhρg / 4

or, T = (0.6 x 0.2 x 0.8 x 980) / 4

or, T = 23.52 dyne/cm