Detecting Radiation (Edexcel GCSE Physics: Combined Science)

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Detecting Radiation

  • It is important to regulate the exposure of humans to radiation
  • The amount of radiation received by a person is called the dose and is measured in sieverts (Sv)
  • One sievert is a very big dose of radiation
    • It would cause acute radiation poisoning

  • People would normally receive about 3 mSv (0.003 Sv) in one year
  • To protect against over-exposure, the dose received by different activities is measured
  • Radiation can be measured and detected using a photographic film or a Geiger–Müller tube

Photographic Film

  • Photographic films detect radiation by becoming darker when it absorbs radiation, just like it does when it absorbs visible light
    • The more radiation the film absorbs, the darker it is when it is developed

  • People who work with radiation, such as radiographers, wear film badges which are checked regularly to monitor the levels of radiation absorbed
  • To get an accurate measure of the dose received, the badge contains different materials that the radiation must penetrate to reach the film
    • These materials may include aluminium, copper, paper, lead and plastic

  • The diagram shows what a typical radiation badge looks like:

Radiation Photographic Film, downloadable IGCSE & GCSE Physics revision notes

A badge containing photographic film can be used to monitor a person’s exposure to radiation

  • The badge shows the amount of different types of radiation that the radiographer has been exposed to
  • Different areas of the film are exposed to different types of radiation
    • Alpha radiation is unlikely to be detected at all as it will be absorbed / stopped by the paper
    • Beta radiation is absorbed by the aluminium
    • Gamma (or X-rays) affect all areas of the film but the lead will reduce some of the gamma radiation

Geiger-Müller tube

  • The Geiger-Müller tube is the most common device used to measure and detect radiation
  • Each time it absorbs radiation, it transmits an electrical pulse to a counting machine
  • This makes a clicking sound or displays the count rate
  • The greater the frequency of clicks, or the higher the count rate, the more radiation the Geiger-Müller tube is absorbing
    • Therefore, it matters how close the tube is to the radiation source
    • The further away from the source, the lower the count rate detected

Geiger-Counter, IGCSE & GCSE Physics revision notes

A Geiger-Müller tube (or Geiger counter) is a common type of radiation detector

Examiner Tip

If asked to name a device for detecting radiation, the Geiger-Müller tube is a good example to giveYou can also refer to it as a GM tube, a GM detector, GM counter, Geiger counter etc… (The examiners will allow some level of misspelling, providing it is readable)Don’t, however, refer to it as a ‘radiation detector’ as this is too vague and may simply restate what was asked for in the question.

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Ashika

Author: Ashika

Expertise: Physics Project Lead

Ashika graduated with a first-class Physics degree from Manchester University and, having worked as a software engineer, focused on Physics education, creating engaging content to help students across all levels. Now an experienced GCSE and A Level Physics and Maths tutor, Ashika helps to grow and improve our Physics resources.