Energy needed in breaking a drop of radius R into n drops of radii r is given by
4πT(nr2-R2)
43π(r3n-R2)
4πT(R2-nr2)
4πT(nr2+R2)
Energy needed = Increment in surface energy = (surface energy of n small drops) - (surface energy of one big drop)
= n4πr2T-4πR2T = 4πT(nr2-R2)