J.J. Thomson had performed discharge tube experiment in a laboratory by subjecting the electric and the magnetic fields on the cathode rays. J.J.Thomson used the experimental results for defining the various properties of electrons, cathode rays.
J.J.Thomson cathode ray experiment
J.J.Thomson used a glass tube called as discharge tube. It is a closed tube of length about 30 cm and diameter of about 4 cm. It is fitted with two metal electrodes named as anode A and cathode C. A side tube P is used to pump out the enclosed gas so as to obtain the desired low pressure. A very high potential is applied across anode and cathode by using the induction coil. Anode is connected to the positive terminal and the cathode is connected to the negative terminal of the high voltage supply source. When a high potential difference is maintained across the electrodes of the discharge tube at a pressure about 0.01 mm of mercury, the Crookes dark space fills the whole length of the tube. This expansion of the dark space is accompanied by fluorescence of the glass walls of the discharge tube. This shows that something is coming out from the cathode, travelling through the length of the tube and falling on the walls. This something is a stream of fast moving electrons and are called cathode rays.
Properties of cathode rays by J.J.Thomson cathode ray experiment
The main properties of the cathode rays are as follows:
(i) The cathode rays are emitted normally from the surface of the cathode. Their direction is independent of the position of the anode.
(ii) Cathode rays travel in straight lines and cast sharp shadows of the obstacles placed in their path.
(iii) Cathode rays exert mechanical pressure on the object they strike.
(iv) Cathode rays carry a large amount of energy and produce heat energy when they strike an obstacle.
(v) When cathode rays fall on certain substances they cause fluorescence.
(vi) Cathode rays affect the photographic plates.
(vii) When the cathode rays strikes the heavy metal, the X rays are produced.
(viii) Cathode rays ionize the gas through which they pass.
(ix) Cathode rays can penetrate the thin foils of metals.
(x) Cathode rays can be deflected by the electric and magnetic fields.