Ionising Radiations (AQA GCSE Combined Science: Synergy: Life & Environmental Sciences): Revision Note

Ionising Radiation

What is ionisation?

• Ionising radiation has enough energy to remove outer electrons from atoms

• When an electron is removed, the atom becomes a charged particle called an ion

• Ionising radiation can also break up molecules

When radiation passes close to atoms it can knock out electrons, ionising the atom

Types of ionising radiation

• Examples of ionising radiation include:

  • Ultraviolet (UV) waves

  • X-rays

  • Alpha particles

  • Beta particles

  • Gamma rays

• Their hazardous effects depend on the type of radiation and the size of the dose

Ionising power

• Alpha radiation is the most ionising

• It has a charge of +2, so it strongly attracts electrons from nearby atoms

• Beta radiation is moderately ionising

• Gamma radiation is the least ionising

  • It has no charge, so it interacts less readily with matter

Range in Air

• The more ionising a form of radiation is, the sooner it will react with the air it is moving through

• Strongly ionising radiation has the shortest range in air

  • Alpha only travels a few centimetres in air

  • Beta has a range of a few tens of centimetres

  • Gamma is not absorbed by air and so has an infinite range, although it does get less intense with distance

Radiation dose

• Radiation dose is a measure of the risk of harm from exposure to radiation

• Radiation dose is measured in Sieverts (Sv)

• 1 Sv = 1000 millisieverts (mSv)