Radioactive Decay
Radiation is emitted by the nucleus of an atom. Un unstable nucleus emits radiation in an attempt to become more stable. This is known a radioactive decay.
Nature of the radiation
An alpha particle is a positively charged helium nucleus consisting of two protons and two neutrons. It is a stable particle.
Beta radiation is identified as a stream of high energy electrons i.e. a beta particle is in principle a negatively charged electron. It is formed by a nucleus decay process.
Gamma radiation is identified as high frequency electromagnetic radiation i.e. they are electromagnetic waves of very short length.
Ionising power
When a particle, such as an alpha or beta, moves at a high speed and collides with an atom, an electron may be ejected from the atom producing a charged ion. Alpha particles have the greatest ionising power followed by beta particles and gamma rays. α > β > γ
Penetrating power
Gamma rays are the most penetrating, having a range of a few hundred meters and can only be withheld by a 2cm- thick lead shield.
Beta particles come second which have a range of a several in air but can be stopped by a 5mm- thick aluminium sheet.
Alpha particles can easily be stopped by a sheet of paper with a range of only a few centimetres in air. γ > β > α
Deflection by electric and magnetic fields
The deflection by electric fields show that alpha particles are positively charged, beta particles are negatively charged and gamma rays are neutral.