1. α particle produce flourescene in zinc sulphide over a thin glass disc. A significant point was that the floursent disc does not show emission of light uniformly but only a series of scintillations, showing that α rays consists of particles which can be counted.
2. α particles are doubely ionized helium atoms. The speed of α particles is about c/100; c (= speed of light).
3. α particles ionize heavily the gases through which they travel.
4. They are easily absorbed by matter.
5. They are scattered while passing through metal sheets.
6. They can produce artificial disintegration of an atom.
7. α particles are chaaracterized by the fact that after they have proceeded a certain distance in air, they are no longer able to ionize the air. This is expressed by saying that they have a well defined range. The range, R is related with the velocity ‘v’ of the particle by the relation
v3 = kR (empirical relation)
The range represents the distance α particles travel before their velocities are reduces by numerous collisions to such a low value that they are no longer capable of ionizing the atoms of the gas concerned. The range ‘R’ of α particles can be very easily and accurately determined experimentally.
