1. The problem statement, all variables and given/known data Describe a method by which the charge / mass ratio e / m of the electron has been determined. Calculate the deflection sensitivity (deflection of spot in mm per volt potential difference) of a cathode ray tube from the following data: electrons are accelerated by a potential difference of 5.0 kV between cathode and annode; length of deflector plates = 2.0 cm; separation of deflector plates = 5.0 mm; distance of mid point of deflector plates from screen = 15.0 cm. Answer: 6 * 10-2 mm V-1. 2. The attempt at a solution I found E = V / d = 5000 / 0.005 = 1 000 000 V and that's it. Not much clear or basic information on the deflection of spot in mm / V can be found online. And I don't think it's as easy as 5 mm / 5000 V.