An electron enters the region between two horizontal plates charged uniformly, but with opposite signs. Its initial velocity, halfway between the plates, is 2 106 ?i m/s. The plates are 4 cm long and 1.6 cm apart. It is considered that, in the whole region between the plates, the electric field is uniform and perpendicular to the plates. (a) What is the maximum modulus that the vertical electric field can have so that the electron does not touch any of the plates? The trajectory of the electrons for this case is illustrated in the second figure.