An electron is moving under the influence of the electric field of a uniformly charged infinite plane sheet s having surface charge density $+\sigma$. The electron at $t=0$ is at a distance of 1 m from s and has a speed of $1 \mathrm{~m} / \mathrm{s}$. The maximum value of $\sigma$ if the electron strikes S at $\mathrm{t}=1 \mathrm{~s}$ is $\alpha\left[\frac{\mathrm{m} \epsilon_0}{\mathrm{e}}\right] \frac{\mathrm{c}}{\mathrm{m}^2}$ the value of $\alpha$ is