The discovery of electrons is related to the experimental study of cathode rays, starting from the discharge phenomenon of vacuum tubes. As early as 1858, German physicist Pique discovered cathode rays while studying gas discharge with a discharge tube. Pluck used a vacuum pump and found that as the air in the glass tube became thinner to a certain extent, the discharge in the tube gradually disappeared. At this time, green fluorescence appeared on the glass tube wall opposite to the cathode. When the magnetic field applied outside the tube changes, the position of fluorescence will also change. It can be seen that this fluorescence is produced by the radiation emitted by the cathode hitting the glass tube wall.
What exactly is cathode ray? /kloc-in the last 30 years of the 0/9th century, many physicists devoted themselves to research. At that time, British physicist crookes and others had proposed that cathode rays were negatively charged particles according to the fact that cathode rays were deflected in the magnetic field. According to the deflection, the charge-to-mass ratio (E/M) of cathode ray particles is 1000 times larger than that of hydrogen ions. At that time, Hertz and his student Leonard added an electric field perpendicular to the cathode ray tube, trying to observe its deflection in the electric field, so they thought the cathode ray was uncharged. In fact, because the vacuum degree is not high, the electrostatic field cannot be established.
J·J· Thomson has designed a new cathode ray tube (pictured above). Under the action of electric field, the cathode ray emitted by cathode C passes through the electric field between another pair of electrodes D and E after focusing by α and B, and a transverse deflection scale is attached to the right tube wall. He repeated the Hertz electric field deflection experiment and didn't see any deflection at first. However, he analyzed that the reason why there was no deflection may be that the electric field could not be established. So, he used the most advanced vacuum technology at that time to obtain a high vacuum, and finally made the cathode ray deflect stably in the electric field, which clearly showed that the cathode ray was negatively charged. He also applied a magnetic field perpendicular to the electric field and the ray velocity (this magnetic field was generated by the coil outside the tube). When the electric field force eE is equal to the Lorentz force evB of the magnetic field, the ray can hit the center of the pipe wall without deflection. According to the calculation, the charge-mass ratio of cathode ray particles is e/m ≈ 10 1C/kg. Through further experiments, Thomson found that by using different materials or changing the gas type in the tube, the charge-to-mass ratio E/M of radiation particles remained unchanged. It can be seen that this kind of particle is a common component in various materials.
1898, Thomson and his students continued to do research on directly measuring the charge of charged particles. One time, the electronic charge of1.1x10-19c was measured by Wilson cloud chamber, which proved that the mass of electrons is about one thousandth of that of hydrogen ions. Thomson finally solved the mystery of cathode ray. Later, many scientists measured the charge value of electrons more accurately, among which American scientist Millikan measured the charge value of electrons for the first time in 1906, e = L.34x 10- 19c. 19 13 finally measured e =1.59x10-19c. It was a high-precision measurement. Modern accurate electron charge E = 1.602 17733 (49