If the excess pressure inside a soap bubble is balanced by an oil column of height of \(2\) mm, then the surface tension of the soap solution will be: (radius of the soap bubble, \(r=1\) cm and density of oil, \(d=0.8\) gm/cm³)
1. \(3.9\) N/m
2. $3.9\times {10}^{-2}$ $\mathrm{N}/\mathrm{m}$
3. $3.9\times {10}^{-3}$ $\mathrm{N}/\mathrm{m}$
4. \(3.9\) dyne/m

The energy needed to break a drop of radius R into n drops of radii r is given by:

1. $4\mathrm{\pi T}({\mathrm{nr}}^2-{\mathrm{R}}^2)$

2. $\frac{4}{3}\mathrm{\pi }({\mathrm{r}}^3\mathrm{n}-{\mathrm{R}}^2)$

3. $4\mathrm{\pi T}({\mathrm{R}}^2-{\mathrm{nr}}^2)$

4. $4\mathrm{\pi T}({\mathrm{r}}^2\mathrm{n}+{\mathrm{R}}^2)$