Cathode Rays: the Electron
High voltage applied across two electrodes in a partially evacuated glass tube produces an electric current and light in the tube.
If we use good vacuum a yellowish green glow is visible from one end of the glass tube
indications that rays were coming from the negative electrode (cathode -rays)
- deflected by electric and magnetic field as negatively charged particles
- fluorescent screen glowed wherever it was struck by the cathode rays
- if no electric or magnetic field is applied, thet travel in straight lines
J.J. Thomson studies quantitatively the deflection of the cathode rays
- measures the charge-to-mass ratio (independent of the gas and electrodes) 1800 times smaller than the one for the known ions!!!
- It should be a new particle! Thomson propose that is the constituent of the atoms. Named: ELECTRON
- Thomson proposes that it has the charge of the Hydrogen ion, and a mass 1800 smaller than that