Thomson’s cathode ray tube experiments were a series of three tests that determined the existence of electrons. Thomson used the experiments, beginning with his invention of the cathode ray tube, to better understand the characteristics of an atom.
Thomson began his experiments by building a cathode ray tube to measure electricity and magnetism. He proved that negative charges, electrons, and positive charges are related. His second experiment involved a modified cathode ray tube with a fluorescent coating, vacuum, and two electric plates, and it further proved electrons' existence. Thomson’s last experiment presented the groundbreaking idea that cathode rays are made from particles inside the atom.