Q.

An electron is moving under the influence of the electric field of a uniformly charged infinite plane sheet S having surface charge density +σ. The electron at t = 0 is at a distance of 1 m from S and has a speed of 1 m/s. The maximum value of σ if the electron strikes S at t = 1s is α[mε0e]Cm2, the value of α is _________ .         [2024]


Ans.

(8)

Initially the electron must move away from sheet

Electric field due to infinite plane sheet of charge,

E=σ2ε0

Force experienced by the electron towards the sheet, F=eE

Hence, acceleration of the electron, a=Fm

a=eEm=eσ2ε0m

Using s=ut+12at2

-1=1×1+12(-eσ2ε0m)12

eσ4ε0m=2σ=8ε0me