Particles and radiation

• Types of ionising radiation

  • Alpha particle
  • Beta
  • Gamma
• Alpha particle

  • Consists of 2 neutrons and 2 protons and is equivalent to a helium nucleus
  • High ionising but low penetrating power
  • Range is 1 to 2 centimetres of air
• Beta


  • A high-speed electron ejected from the nucleus as a neutron turns into a proton
  • Medium ionising and penetrating power
  • Range is approximately 15 centimetres of air
• Gamma

  • Electromagnetic radiation from the nucleus
  • Low ionising and high penetrating power
  • Range is many kilometres of air
• Each type of radiation shown in the electromagnetic spectrum has a different wavelength and a different frequency
• Half-life

  The time taken for half of the unstable nuclei in sample to decay
• What the half-life of a radioactive element is the time taken for

  • The activity to halve
  • The number of parent nuclei to halve
  • The mass of the parent nuclei to halve
• The use of the international system of units (SI) relevant to health:

  • Kilogram (kg) → mass
  • Metre (m) →length 
  • Second (s) → time

  How to convert units of measure: 

  • Metres to millimetres 
  • Millimetres to micrometres 
  • Litres to millilitres 
  • Millilitres to microlitres 
  • Grams to milligrams 
  • Milligrams to micrograms

  The importance of using significant figures and science notation:

  • Makes calculation with large or small numbers less cumbersome
  • Reduces the chances of data errors