Ionising Radiation & Detectors (OCR AS Physics): Revision Note

Ionising Radiation & Detectors

• Ionising radiation include alpha, beta and high-energy electromagnetic radiation such as X-rays, gamma rays and UV

• They are used in smoke detectors and in many medical applications, such as:

  • Disinfecting medical instruments

  • X-rays

  • Radiotherapy

  • CT scans

• These normally use X-rays, gamma rays or radioactive tracers

• In those areas of industry and medicine, where people are routinely working with ionising radiations, various safety procedures are put in place

• Workers are routinely monitored to check the levels of radiation that they are exposed to and strict limits are placed on what they can receive

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

• Limits are often placed on the amount of time that workers can spend using radioactive materials.

• Where feasible, barriers will be placed between the worker and the source in order to absorb the radiation

  • Doctors, for example, will leave the room whilst carrying out certain procedures (including x-rays) in order to minimise exposure.

• Areas or containers that pose a radiation hazard should have the appropriate radiation hazard symbol

Radiation hazard symbol

• The universal radiation symbol is important, so people that speak any language can still understand its meaning

Radiation Detectors

• Radiation can be detected by a Geiger-Müller tube, or a geiger counter

• Geiger-Müller tubes are simple devices that detect the presence of the ions created by radiation entering the tube

• Connecting the tube to a counter allows the amount of radiation to be determined

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

• The amount of radiation given off by an isotope each second is known as its activity and is measured in becquerels (Bq)

• An activity of one becquerel means that there is one decay per second