ANODE RAYS OR CANAL RAYS
E. Goldstein, a German scientist, in 1886 , discovered the existence of a new type o rays in the discharge tube. He used a perforated cathode (Fig. 5.5) in the discharge tube. The cathode divided the discharge tube in two chambers. On passing the electric discharge at low pressure he observed a new type of rays streaming behind the cathode. The path of these rays became visible due to the glow of the residual gas. These rays also produced fluorescent glow on striking the walls of the tube behind cathode. These rays were named anode rays or canal rays. These rays were named canal rays because they passed through ‘holes’ or ‘canals’ in the cathode.
Fig. 5.5. Canal rays.
Further investigations of these rays showed that they consist of positively charged material particles.
Some of the characteristic properties of anode rays are:
- Anode rays consist of material particles.
- Anode rays are deflected by electric field towards negatively charged plate. This indicates that they are positively charged.
- The charge to mass ratio of the particles in the anode rays was determined by W. Wien by using Thomson’s technique. Charge to mass ratio of the particles in the anode rays depends upon nature of the gas taken in the discharged tube.
DISCOVERY OF THE PROTON
As already mentioned, the charge to mass ratio of the particles in .the anode rays was found to depend upon the nature of the gas in the discharge tube. It was observed that elm ratio was maximum when hydrogen gas was taken in the discharge tube. This indicated that positive ions formed from hydrogen are lightest. These lightest positively charged particles were named protons. The charge and mass of the proton were determined, in the same manner as the one discussed in case of electron. Charge to mass ratio for protons was found to be 9.58 x 107 C/kg. Charge on proton is opposite but equal in magnitude to the charge on the electron i.e. 1.60 X w-19 c. From these two observations mass of a proton works out to be 1.67 x 10-27 kg. It is practically the same as the mass of a hydrogen atom and is about 1837 times the mass of an electron.
In general, a proton is represented as p +.
A proton is a fundamental particle of atom carrying one unit positive charge and having mass nearly equal to the mass of an atom of hydrogen.