The line $\mathrm{AA}\text{'}$ is on a charged infinite conducting plane which is perpendicular to the plane of the paper. The plane has a surface density of charge $\sigma$ and $\mathrm{B}$ is a ball of mass $\mathrm{m}$ with a like charge of magnitude $\mathrm{q}$. $\mathrm{B}$ is connected by a string from a point on the line $\mathrm{AA}\text{'}$. The tangent of the angle $\left(\mathrm{\theta }\right)$ formed between the line $\mathrm{AA}\text{'}$ and the string is (provided, the charge $\mathrm{q}$ does not affect the distribution of charge on conducting plate)