I also agree that the Millikan oil drop experiment is what demonstrated the particle-like nature of electrons, not Thomson's work. The issue is that he seemed to start with the presupposition that cathode rays were made of particles (nothing wrong with that as long as you are clear about it), so we can't really cite his work as the first evidence that the cathode ray really did consist of particles. Kaufmann concluded that the hypothesis that cathode rays were particles was inconsistent with this result. Thomson's work is invalid, because finding the charge-to-mass ratio was extremely important. Thomson found that cathode rays always had the same e/m ratio, no matter what metals were used for the cathodes and no matter what gas was used in the tubes. His work doesn't seem to rule that possibility out.Īm I missing something here? Note that I am not saying J. By thinking in terms of a force density on the so-called fluid, we could work out the ratio of densities ρ_q/ρ_m by following the same work that J. The issue is that I can conceive that the cathode ray is some sort of continuous charged fluid with charge density ρ_q and mass density ρ_m. Thomsons experiments with cathode-ray tubes revealed that all atoms contain tiny negatively charged subatomic particles or electrons. Thomson presupposed that the cathode ray consisted of a stream of particles, and worked his way to calculate the charge-to-mass ratio e/m of an electron assuming it is a discrete particle. Thomson's work indicates that the charge and/or mass is quantized. As far as I can tell, this was only demonstrated in the Millikan oil drop experiment later in 1909. However, in order for that to be the case, there has to be evidence that the mass and/or charge is quantized. Thomson provided evidence that the cathode ray consists of a stream of particles and thus he demonstrated the existence of electrons around 1897. He built his cathode ray tube with a metal cylinder on the other end. In almost every video and webpage I visit, I see people claiming that J. Thompson, conducted his first cathode ray tube experiment to prove that rays emitted from an electron gun are inseparable from the latent charge. ![]() I am trying to make a quick sanity check.
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