a beam of electrons moving with a velocity 1.0x10⁷ms^-1enters midway between two horizontal plates in a direction parallel to plates. plates r 5cm long, 2cm apart & have a p.d V applied between them. cal the value of V if beam is deflected so that it jst grazes the edge of lower plate ? e/m=1.8x10¹¹Ckg^​-1