Two soap bubbles of radii r1 and r2,r1>r2 get attached to each other to have a common interface. The radius of this interface is

. Let r be the radius of common interface. ThenP1−P=4Tr1  and  P2−P=4Tr2 ∴ P2−P1=4T1r2−1r1 Further  P2−P1=4Tr From eqs. (1) and (2), we get 4Tr=4T1r2−1r1=4πr1−r2r1I2 r=r1r2r1−r2