A soap bubble of radius 1 cm expands into a bubble of radius 2 cm. Calculate the increase in surface energy if the surface tension for soap is 25 dyne/cm.

Explanation

Surface energy per unit area is equal to surface tension.
E = increase in surface area `xx` ST
`=4pi(2^(2)-1^(2))xx2.5`
=`4pixx3xx2.5`
=`1.02xx10^(3)`erg