JEE Mains · Physics · STD 12 - 1. Electric charges and fields
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 \(1 m s ^{-1}\). The maximum value of \(\sigma\), if the electron strikes \(S\) at \(t=1 s\) is \(\alpha\left[\frac{m \epsilon_0}{e}\right] \frac{ C }{ m ^2}\). The value of \(\alpha\) is __________ .
- A 2
- B 4
- C 6
- D 8
Answer & Solution
Correct Answer
(D) 8
Step-by-step Solution
Detailed explanation
\(u=1 m / s ; a=-\frac{\sigma e}{2 \epsilon_0 m}\) \(t=1 s\) \(S=-1 m\) Using \(S=u t+\frac{1}{2} a t^2\) \(-1=1 \times 1-\frac{1}{2} \times \frac{\sigma e}{2 \epsilon_0 m} \times(1)^2\) \(\therefore \sigma=8 \frac{\epsilon_e m}{e}\) \(\therefore \alpha=8\)
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