Final answer:
To calculate how far below the axis an electron has moved, details such as electric field strength, initial velocity, and exposure duration are required. Without these specifications, the calculation cannot be completed.
Step-by-step explanation:
To determine how far below the axis an electron has moved when it reaches the end of the plates, we would need additional information about the conditions within the electric field between the plates, such as electric field strength, the velocity of the electron as it enters the field, and the length of the plates.
The movement of the electron in an electric field is due to the electric force acting on it, calculated by F = qE, where 'F' is the force, 'q' is the charge of the electron, and 'E' is the electric field strength. If we know the duration of time the electron is under the influence of this force, we can use kinematic equations to find the displacement. Without such information, we cannot provide a numerical answer to the question.
Given that the electric force on an electron is directed upwards toward a positively charged plate and the magnetic force (by the Right-Hand Rule) is downward, an electron will undergo a combination of electric and magnetic forces, which influences its trajectory between the plates.