This is all the information that is stated in the question. I asked 5 classmates and no one knows where to begin. In the notes they talk about lenses but it does not specify that is what is doing the focusing.
[b]1. At what angle should a 1kV electron beam with a total current of 1mA leave an electron gun in order that the cross section of minimum diameter will occur on a screen 25cm away? The original diameter of this beam is 2mm.
[b]2. Cannot find equations in book or notes anywhere...