Discovery of proton

Positive Rays:

In 1886, Eugen Goldstein used a discharge tube with a hole in the cathode. He observed that while cathode rays were streaming away from the cathode, there were coloured rays produced simultaneously which passed through the perforated cathode and caused a glow on the wall opposite to the anode. Thomson studied these rays and showed that they consisted of particles carrying a positive charge. He called them positive rays.

Properties of Positive Rays:

Some of the important properties of anode rays are as follows-

  • They travel in a straight line in a direction opposite to the cathode.
  • They are deflected by electric as well as magnetic field in a way indicating that they are positively charged.
  • The charge to mass ratio (e/m) of positive particles varies with the nature of the gas placed in the discharged tube.
  • They cause fluorescence in the zinc sulphide.

It was J.J. Thomson who studied their nature and found that the actual mass of proton is             +1.60 X 10-19 C and has mass equal to that of hydrogen atom. Therefore, “A proton is a subatomic particle which has one unit mass and one unit positive charge i.e. +1.60 X 10-19 C”.

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