The radius of a spherical soap bubble is r and surface tension of soap water is T respectively. Find the charge uniformly distributed over the outer surface of the bubble is required to double its radius. (Atmospheric pressure is $P_o$ and inside temperature of the bubble during expansion remain constant)

• A

  $8\mathrm{\pi r}{\left[{\mathrm{ϵ}}_0\mathrm{r}\left(7{\mathrm{P}}_0\mathrm{r}+16\mathrm{T}\right)\right]}^{1/2}$

• B

  $4\mathrm{\pi r}{\left[{\in }_0\mathrm{r}\left(7{\mathrm{P}}_0\mathrm{r}+8\mathrm{T}\right)\right]}^{1/2}$

• C

  $\mathrm{\pi r}{\left[{\in }_0\mathrm{r}\left(7{\mathrm{P}}_0\mathrm{r}+12\mathrm{T}\right)\right]}^{1/2}$

• D

  $8\mathrm{\pi r}{\left[{\mathrm{ϵ}}_0\mathrm{r}\left(4{\mathrm{P}}_0\mathrm{r}+12\mathrm{T}\right)\right]}^{1/2}$