Question

The surface energy of a drop of water of radius $r$ is proportional to:

• A. $r^3$
• B. $r^2$
• C. $r$
• D. $\frac{1}{r}$

Answer 1

The correct option is B $r^2$

We know,
Surface tension $=\frac{\text{Surface energy}}{\text{Unit Area}}$

$\therefore$ Surface energy $\propto$ Area $\propto$ $r^2$
Option (b) is correct.