Define surface energy. Find the relation between surface energy and surface tension.

Explanation

Surface energy
It is the potential energy per unit area. The SI unit of surface energy is `Jm^(-2)`
Let us consider a frame PQRS with soap film produced on it. Force on frame due to surface tension S is
`F=Sxx2l`
Here 2 is multiplied because liquid film has two surfaces. Work done to displace film by small distance is given by
`W=Fx=2Slx`
`:.("Work done")/("Surface area")=(2Slx)/(2lx)S` [ `:.` Increased area A=2lx]
Since work done is equal to potential energy,
So `(P.E.)/("Surface area")` = Surface energy = Surface tension.