Ionising radiation

Ionising radiation

1. Alpha particles are helium nuclei.

   • An alpha particle if 2 neutrons and 2 protons - The same as a helium nucleus.
   • They are relatively big, heavy and slow moving
     • They therefore don't penetrate very far into materials and are stopped quickly, even when travelling through air.
       • A piece of paper or 5cm of air will stop it.
   • Because of their size they are strongly ionising, which just means they bash into a lot of atoms and knock electrons off them before they slow down.
     • This creates lots of ions - hence the term ionising.

2. Beta particles are electrons.

   • Beta particles are in between alpha and gamma in terms of their properties.
   • They move quite fast and are very small (the same size as a normal electron).
   • They are penetrate moderately into materials before colliding have a long range in air, and are moderately ionising too.
     • A piece of aluminum 5mm thick or 1m of air will stop it.
   • For every beta particle emitted, a neutron turns into a proton in the nucleus.
   • A beta particle is simply an electron, with virtually no mass and a charge of -1.

3. Gamma rays have a very short wave length, they are essentially an electromagnetic wave.

   • Gamma rays are the opposite to alpha particles in terms of their properties.
   • They penetrate far into materials without being stopped and pass straight through air.
     • Only 1m of concrete and no amount of air will stop it.
   • They are weakely ionising because they tend to pass through rather than collide with atoms. Eventually they do hit something and do damage.
   • Gamma rays have no mass and no charge.