J.J. Thomson discovered the electron because electrons are negatively charged after observing the CRT reaction to a magnetic field/electromagnetic field. If that is the case, wouldn't the charged electrons in the ray repel each other? Note that I am referring to simple experiments where there is only a cathode in one side and an anode on the other side of a tube. No electromagnetic coils are used on these experiments, yet the ray remains straight or at least whole and relatively uniform across the beam. Is there a relativistic or quantum mechanic explanation for how the electrons stay aligned? Is this due to a property of the electromagnetism and how waves behave?
Electrons in a beam DO repel each other. In order to focus in a cathode ray tube, tricks are employed (axial magnetic field) that cause convergence at the screen surface. The beam originates at a point, diverges, then reconverges.