Question

Prove excess of pressure inside any bubble is double that of inside a drop. Please explain.

Answer 1

Consider a soap bubble of radius R and surface tension T. There are two free surfaces of soap bubble. Due to surface tension, the molecules on the surface film experience the net force in the inward direction normal to the surface.The pressure due to surface tension can be calculated by imagining you cut the object in half. You will end up with either one (a droplet) or two (a bubble) circles of surface. Multiply the surface tension with the total length of the surface circles  (2πr2πr or 4πr4πr, and then you can calculate the pressure by dividing that force by the surface of the circle πr2πr2.