$S=$ surface tension of soap Liquid
$1=$ length of $\mathrm{PQ}$
Total Inward Force on the wire P Q
$$
F=S \times 21
$$
To increase surface area we have to pull wire $\mathrm{P} \mathrm{Q}$ outwards with for $\mathrm{F}$ Film is stretched by small distance $x$ to position $P, Q$
To increase in Area of film $\mathrm{P} \mathrm{Q} \mathrm{Q}, \mathrm{P}$,
$$
=\mathrm{a}=2(1 \times \mathrm{x})
$$
Work done in stretching film $\mathrm{F}=\times$ Distance
$$
\begin{array}{l}
=(s \times 21) \times x=s \times(2 l x)=s \times a \\
2 l x=\text { increase in area =a }
\end{array}
$$
$1 \times$ a $=$ area $o^{+}$film Both side
Surface Energy is defined as the amount of workdone against the force of surface tension, in forming the liquid surface of a given area at a contant temprature