89.

What are anode rays? How do they originate? Briefly explain their important properties.

The streams of positively charged particles are called anode rays or positive rays or canal rays.
In 1886, Goldstein performed a discharge tube experiment, using perforated cathode. He observed that in addition to cathode rays, a new kind of rays were also found. These rays passed through the hole of the perforated cathode but travelled in a direction opposite to that of cathode rays. These rays were found to consist of positively charged particles and were called anode rays or positive rays or canal rays.

These rays are believed to be produced as a result of the knock out of the electrons from the gaseous atoms by the bombardment of high speed electrons of the cathode rays on them. Thus(anode rays are not emitted from the anode but are produced in the space between the anode and the cathode. In other words anode rays (or positive rays) are atomic or molecular residues from which some electrons have been removed. The removed electrons constitute the cathode rays and positive residues form the positive or canal rays.

Properties of anode rays:
(i) Anode rays travel in a straight line.
(ii) These rays are deflected by electric and magnetic fields in a way that shows that these rays are positively charged particles. For example, these rays are attracted towards the negative plate in the electric field which means rays are positively charged particles.
(iii) These rays consist of material particles and rotate the paddle wheel placed in their path.
(iv) Anode rays produce heating effect when struck against a metal foil.
(v) Hie ratio of charge to mass (^e/_m) for positive rays is considerably smaller than for electrons and is not constant but depends on the nature of the gas taken in the discharge tube. In other words, the value of ^e/_m for a positive ion depends upon the charge of the ion and its mass.