First of all, if this electric field is not superimposed with a magnetic field, the horizontal velocity will not change when moving in the electric field; The velocity in the vertical direction should be analyzed. Generally, gravity is downward and electric field force is upward. If your teacher is normal, the values of gravity and electric field force will be equal, so they will cancel out. If your teacher is abnormal, there will be synergy. If the electric field force is greater than gravity, electrons will deflect upward, otherwise they will deflect downward. After flying out of the electric field area, continue to decompose the velocity orthogonally, and the velocity in the horizontal direction remains unchanged, and the vertical direction is only affected by gravity, just like a free fall, but with the initial velocity, the velocity in the last two directions can be calculated by synthesizing the velocity component vectors. If your teacher is a little more abnormal, he will put a rake at a distance d outside the electric field. At this time, the vertical deflection distance needs to be divided into two parts. In the first part, in the electric field area, only the vertical component is multiplied by the time in the electric field (time is obtained by dividing the length of the electric field by the horizontal speed), and in the second part, only the vertical component is multiplied by the time outside the electric field (time is obtained by dividing the horizontal speed), and then the two are added. Ps: Deflection angle is the inverse trigonometric function arctan (vertical velocity divided by horizontal velocity at the moment of vertical emission electric field), that is, the included angle between vertical velocity and horizontal velocity at the moment of vertical emission electric field.

If the magnetic field is superimposed, then Lorentz force should be considered, and Lorentz force will generally cancel Lorentz force and gravity (Lorentz force is calculated at horizontal speed). If you don't cancel it, you can use the dynamic equation to solve it, but that's the content of the university. Your teacher won't be so abnormal, will she?