What did the cathode ray tube tell us about atomic structure?
When J.J. Thompson studied cathode ray tubes in 1895, he realized that the resulting rays were little more than streams of negatively charged particles. By bending the rays with a magnetic source and then measuring energy of the rays he could deduce the average mass per charge ratio of the particles in the tube. The ratio he uncovered was over a thousand times smaller than the known ratio of a hydrogen ion (aka proton) meaning it most be orders of magnitude smaller. This particle turns out to be what is now known as the electron.
