A number of droplets, each of radius r, combine to form a drop of radius R. If T is the surface tension, the rise in temperature will be

43πR3=n×43πr3  or  R3=nr3Energy evolved =n×4πr2−4πR2TNow, θ=QVρS=QV=( In C.G.S. system, ρ=1 and S=1)∴ θ=n×4πr2−4πR2T43πR3=3Tnr2−R2R3=3Tnr2nr3−R2R3=3T1r−1R