Ionising Radiation (T7) Flashcards
Describe alpha radiation..
Alpha radiation consists of fast moving particles thrown out of fast moving nuclei when they decay.
These are called alpha particles.
Alpha particles are Helium nuclei - helium atoms without their orbiting electrons.
They have a relatively large mass and are made up of 4 nucleons and so have a mass number of 4.
They are also charged because of the two protons that they carry, giving them a relatice charge of +2.
They have a short range; the range of ionising radiation is the distance that it can travel through matter. Alpha particles can only travel a few centimetres in air and cannot penetrate more than a few mm of paper.
The limitied range is because they interact with atoms along their paths, causing ions to form, meaning they rapidly give up the energy that they had when they were ejected from the unstable nucleus.
Describe beta radiation..
Very fast moving electrons ejected by a decaying nucleus.
Beta decay involves a neutron in the nucleus splitting into a proton and and and electron. The proton remains in the nucleus and the eletcron is ejected at high speed as a beta particle.
They are very light with only 0.000125 times the mass of an alpha particle.
The relative charge of a beta particle is -1.
Beta particles interact with matter in their paths less than alpha particles because they are small and carry less charge.
This means they have a greater range, can travel long distances through air, pass through paper easily and are only absorbed by denser materials like aluminium (a mm or two of aluminium will stop all but the most energtic beta particles)
Describe gamma rays..
Electromagnetic rays with very short wavelengths.
As they are waves they have no mass and no charge.
Weakly ionising and only intereact with atoms in their paths very occasionally.
Extremely penetrating and pass through all but the very densest materials with ease.
It take several cm of lead or a metre of concrete to stop gamma radiation.
Gamma radiation is emitted in packets of energy called photons.
