Using radioactivity

• Give example uses of radioactivity

  1. Household fire alarms (smoke)
  2. irradiating food
  3. Sterilisation of equipment
  4. Tracing and gauging thicknesses of materials
  5. Diagnosis and treatment of cancer
• How do smoke alarms work?


  1. A radioactive substance is in the alarm which emits alpha radiation.
  2. The emitted alpha particles ionise the air in the detector and cause a current to flow between the plates
  3. when smoke interferes with radiation, the air is no longer ionised and so no current can flow.
  4. This reduction in current flow triggers the alarm
• how is beta radiation used to determine thickness?

  1. A beta source is placed above the material and a detector is placed below it.
  2. If there is an increase in radiation detected by the detector, too much radiation is passing through the material, and so it is too thin
  3. If there is a decrease in radiation is detected, then the material blocks too much radiation, and so it is too thick.
• why is ionising radiation dangerous?

  1. It can damage tissues and kill cells
  2. It can cause mutations
• What is a consequence of cell mutation?

  Cancer
• What precautions should people take when using ionising radiation?

  1. Avoid handling the source directly (use tongs)
  2. Wear radiation protective clothing
  3. Keep the radiation in lead containers to reduce the amount of radiation that can escape
  4. Keep exposure time to a minimum
• Does a long half life or a short half life make a source more dangerous?

  If it has a long half life then it would remain highly radioactive for longer therefore making it more dangerous
• what is radioactive contamination?

  The presence of unwanted radioactive nuclei on other materials
• What is irradiation?

  1. The process of exposing a material to nuclear radiation
  2. The material does not become radioactive.
• what happens when food is irradiated?

  Makes it safer to eat and it can be stored for longer before going off.
• Why is surgical equipment sealed into bags before irradiation?

  As gamma rays pass through the packaging and syringe, they will kill viruses and bacteria which contaminate the syringe. 
• why are gamma sources used as tracers rather than beta sources?

  They mostly just pass through the body without causing too much ionisation in our cells.
• What type of radiation is produced by americium-241?

  Alpha particles