An electron (charge = e, mass = m) is projected horizontally into a uniform electric field produced between two oppositely charged parallel plates, as shown in figure. The charge density on both plates is `+- sigma C//m^2` and separation between them is d. You have to assume that only electric force acts on the electron and there is no field outside the plates. Initial velocity of the electron is u, parallel to the plates along the line bisecting the gap between the plates. Length of plates is 2L and there is a screen perpendicular to them at a distance L. (i) Find s if the electron hits the screen at a point that is at same height as the upper plate.
(ii) Final the angle q that the velocity of the electron makes with the screen while it strikes it.

Answer

(i). `sigma=(epsilon_(0)m du^(2))/(8eL^(2))`
(ii). `theta=tan^(-1)((epsilon_(0)m u^(2))/(2Le.sigma))`