P2 - Types of radiation
Radioactive materials - substances that give our nuclear radiation.
Nuclear radiation - used in medical treatments such as Radiotherapy to cure cancer. - Nuclear radiation can kill the cancer cells - can also kill healthy cells.
Radioactivity - change in structure of radioactive atom and the release of one of the three types of nuclear radiation:
- alpha ()
- beta ()
- gamma ()
Nuclear radiation can cause ionisation, producing postively and negatively charged ions when atoms gain or lose electrons. Ionisation can be harmful inside the body - damages cells and can initiate chemical reactions by breaking molecular bonds.
- smoke detectors - contain americium-241 - emits alpha radiation. The emitted alpha particles cause the ionisation of air particles. The positive and negative ions formed are attracted to oppositely charged electrodes in the detector -> current flowing in the circuit.
Smoke enters -> less ionisation -> alpha particles absorbed by smoke particles -> smaller current flows -> alarm sounds
- strong ionising power
- absorbed by a few cm of air or a thin sheet of paper
Tracers - a beta-emitter tracer can be used for:
- Detecting tumours in certain parts of a patient's body - i.e. brain, lungs
- To identify plants that have been fed with a fertiliser containing a beta particle emitter (can be used to develop better fertilisers)
- In a paper thickness gauge - if paper thickness is too great, more beta radiation is absorbed and less passes through to the detector. A signal is then sent to the rollers to move closer together, which reduces the thickness of the paper.
- Reasonable ionising power
- Passes through air and paper - absorbed/stopped by a few mm of aluminium
- To treat cancer - destroys cancerous cells.
- To sterilise medical equipment - destroys microorganisms. No heat required - minimises damage.
- Non-destructive tests can be carried out on welds - any cracks or defects the rays can get through
- Very penetrating, needs many centimetres of lead or many metres of concrete to absorb most of it.
- Poor ionising power