Discovery of Proton

In 1886, E.Goldstein discovered an entirely different types of rays in the discharge tube.
He observed that if a perforated disc cathode was used in place of the plane disc cathode, and the gas pressure was not too low, coloured rays emerged on the opposite of the anode. These rays passed through the holes of the cathode, travelled in the form of a stream or canal and produced a glow on the other end of the discharge tube.
Goldstein called them Canal Rays or Anode Rays.
These rays were found to consist of postively charged particles.
Hence, they are known as Positive Rays.

Properties of Canal Rays

Canal rays posses the following properties.

I) Canal rays travel in a straight line in a direction opposite to the cathode.

ii) In the presence of an electric field, canal rays deflected towards the negative electrode. This indicate that the constituent particles of canal rays are postively charged.

iii) Canal rays are also affected by a magnetic field. In the presence of a magnetic field, these rays deflected in a way which indicates that these are composed of postively charged particles.

iv) The charge to mass ratio (e/m) of the constituent particles of canal rays with the nature of the gas taken in the discharge tube.
v) The mass of a constituent particle of canal rays is roughly 2000 times or more the mass of an electron.
vi) Canal rays produce fluorescence when made to fall on zinc sulphide.

Definition of Proton

On the basis of above discussion, a proton can be defined as follows.
A proton is a sub atomic particles which has a mass equal to 1.672×10^-24g (1 amu) and a positive charge equal to 1.6021×10^-19 coulombs (1unit of charge).

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