When a soap bubble of radius \(0.2 \mathrm{~mm}\) is charged, it experiences an outward electrostatic pressure of magnitude \(\frac{\sigma^2}{2 \varepsilon_0}\), where \(\sigma=20 \mu \mathrm{Cm}^{-2}\) is the surface charge density. If the excess pressure inside the soap bubble due to the surface tension is same as
this electrostatic pressure, then the surface tension of the soap solution is
\[
\left(\varepsilon_0=8.85 \times 10^{-12} \mathrm{C}^2 \mathrm{~N}^{-1} \mathrm{~m}^{-2}\right)
\]

1. A \(8.85 \times 10^{-4} \mathrm{Nm}^{-1}\)
2. B \(12.4 \times 10^{-4} \mathrm{Nm}^{-1}\)
3. C \(11.3 \times 10^{-4} \mathrm{Nm}^{-1}\)
4. D \(90 \times 10^{-4} \mathrm{Nm}^{-1}\)