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

A positively charged electrostatic deflection plate will attract the electron beam. This is because electrons carry a negative charge, and opposite charges attract. When the electron beam, which consists of negatively charged particles, approaches a positively charged plate, the electrostatic force will draw the beam towards the plate. This principle is fundamental to the operation of devices like cathode ray tubes, where the direction and behavior of the electron beam are manipulated by various charged plates.

The attraction occurs due to the nature of electric fields produced by charged objects, where a positively charged plate creates an electric field that directs negatively charged electrons toward it, resulting in a deflection of the beam.