Cathode ray discharge tube experiment : A cathode ray tube is made of glass containing two thin pieces of metal, called electrodes, sealed in it. The electrical discharge through the gases observed only at very low pressure and at very high voltage. The pressure of different gases could be adjusted by evacuation. When sufficient high voltage is applied across the electrodes, current starts flowing through a steam of particles moving in the tube from the negative electrode (cathode) to the positive electrode (anode). These were called cathode rays or cathode ray particles. (Because these emanated from the negative electrode.
- Cathode rays themselves are not visible but their behaviour can be observed with the help of certain kind of materials(fluorescent (or) phosphorescent) which glow when hit by them. Example : Television picture tube.
- Cathode rays start from the cathode and move towards the anode.
- These rays travel in straight lines in the absence of electric and magnetic field.
- In the presence of electric and magnetic field they are deflected in a manner expected for negatively charged particles, suggesting that cathode rays consist of negatively charged particles called “Electrons”.
- These rays were found to be independent of the nature of the cathode materials and nature of the gas present in the cathode ray tube.
Hence, it was concluded that electrons are basic constituents of all the atoms.