A negatively charged electrostatic deflection plate will have what effect on the electron beam?

A negatively charged electrostatic deflection plate will repel the electron beam. This is because electrons carry a negative charge, and like charges repel each other according to the principles of electrostatics. When the beam of electrons approaches a negatively charged plate, the negative charges on the plate create a repulsive force that pushes the electrons away from the plate. As a result, the electron beam will be deflected in a direction away from the plate, altering its path.

In this scenario, the effect of the negatively charged plate is directly related to the charge of the particles in the electron beam. Since both the electrons and the plate carry the same type of charge (negative), this fundamental interaction results in repulsion, effectively influencing the trajectory of the beam as dictated by the laws of electrostatic forces.