Canal Ray Experiment
Canal Ray experiment is the experiment performed by German scientist Eugen Goldsteinin 1886 that led to the discovery of the proton. The discovery of proton which happened after the discovery of electron further strengthened the structure of the atom. In the experiment, Goldstein applied high voltage across a discharge tube which had a perforated cathode. A faint luminous ray was seen extending from the holes in the back of the cathode.
Apparatus of the experiment
The apparatus of the experiment incorporates the same apparatus as of cathode ray experiment which is made up of a tube made of glass containing two pieces of metals ions at the different end which acts as an electrode. The two metal pieces are connected with an external voltage. The pressure of the gas inside the tube is lowered by evacuating the air.
Procedure of the experiment
- Apparatus as set up by providing a high voltage source and evacuating the air to maintain low pressure inside the tube.
- High voltage is passed to the two metal pieces to ionize the air and make it a conductor of electricity.
- The electricity starts flowing as the circuit was complete.
- When the voltage was increased to several thousand volts, a faint luminous ray was seen extending from the holes in the back of the cathode.
- These rays were moving in the opposite direction of cathode rays and were named canal rays.
When very high voltage is applied, it ionizes the gas and it is positive ions of gas that constitutes the canal ray. It is actually the nucleus or kernel of the gas that was used in the tube and hence it has properties different from the cathode rays which were made up of electrons.
- Unlike cathode rays, canal rays depend upon the nature of gas present in the tube. It is because the canal rays are composed of positive ionized ions formed by ionization of gas present in the tube.
- The charge to mass ratio for the particles of ray was found to be different for different gases.
- The behaviour of particles in an electric and magnetic field was opposite to that of cathode rays.
- Some positively charged particles carry multiples of the fundamental value of the charge.
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