Radioactivity
Radiation: The emission or transmission of energy in the form of waves or particles through space or a medium.
Some isotopes are unstable. To become stable thee nucleus gives out radiation - this is called radioactive decay, it is a random process. Activity: the rate at which a source of unstable nuclei decay measured in becquerels (Bq). You can measure activity with a Geiger-muller tube. The count rate is the number of counts recorded each second by the a detector.
Alpha
Consists of 2 protons and 2 neutrons - helium nucleus.
- Range: 5cm in air.
- Penetrating Power stopped by a single sheet of paper.
- Ionising Power very strongly ionising.
Beta
An electron that is ejected from a nucleus at a very high speed. The electron is formed when a neutron changes into a proton and an electron.
- Range: 15cm in air.
- Penetrating Power stopped by a few millimetres of aluminium.
- Ionising Power fairly strongly ionising.
Gamma
They are a type of electromagnetic radiation given out by the nucleus.
- Range: several meters in air.
- Penetrating Power stopped by several cm of lead.
- Ionising Power weakly ionising.
Neutron
Sometimes a neutron is given out by the nucleus.
Irradiation
Exposure of an object to nuclear radiation. This can be used to sterilise equipment with gamma radiation. The object does not become radioactive as it does not come into contact with the radioactive nucleus just the radiation.
Contamination
When unwanted radioactive isotopes end up on other materials. The object then becomes radioactive.
Background Radiation
- Certain rocks are radioactive such as granite.
- Cosmic rays from space - high energy particles that travel through space and crash into the atmosphere.
- Fallout from nuclear testing.
- Nuclear accidents.
Nuclear Fission
Nuclear fission is when an unstable large nucleus splits, usually the nucleus first has to absorb a neutron. When it splits it forms 2 smaller roughly equal daughter nuclei and emits 2 or 3 neutrons and gamma radiation and energy. The neutrons emitted can be absorbed by more nuclei and cause a chain reaction releasing an enormous amount of energy. A controlled chain reaction can be used in a reactor to release energy. Uncontrolled are used in nuclear weapons.
Nuclear Fusion
2 light nuclei are joined to make a heavier nucleus some of the mass of the nuclei is converted to energy which is released as radiation. This process happens in Stars. It is not a chain reaction.
Uses of Nuclear Radiation
Nuclear Radiation can be used to:
- Explore internal organs.
- Control or destroy unwanted tissue.