Uses of Radioactivity (CIE IGCSE Physics: Co-ordinated Sciences (Double Award))

• Radioactivity has the following applications:
  
  • household fire (smoke) alarms
  • irradiating food to kill bacteria
  • sterilisation of equipment using gamma rays
  • measuring and controlling thicknesses of materials with the choice of radiations used linked to penetration and absorption
  • diagnosis and treatment of cancer using gamma rays

Household fire alarms are a use of alpha radiation

• Alpha particles are used in smoke detectors
• The alpha radiation ionises the air within the detector, creating a current
• The alpha emitter is blocked when smoke enters the detector
• The alarm is triggered by a microchip when the sensor no longer detects the alpha particles

Uses of alpha radiation: household fire alarms

In the diagram at the bottom, alpha particles are stopped by the smoke, preventing the flow of current and triggering the alarm

Sterilisation of equipment using gamma rays

• Gamma radiation is widely used to sterilise medical equipment

Irradiating food to kill bacteria using gamma rays

• Food can be irradiated to kill any microorganisms that are present on it
• This makes the food last longer and reduces the risk of food-borne infections

Uses of gamma radiation: killing bacteria

Food that has been irradiated carries this symbol, called the Radura. Different countries allow different foods to be irradiated

Measuring the thickness of materials using different radiation

• Beta radiation is most commonly used to measure the thickness of materials

• A material moves across the radiation source
  • The particles that penetrate it are monitored using a detector above
• The thickness of the material is monitored
  • If the material gets thicker, more particles will be absorbed by the material, meaning that less will get through and be detected by the detector
  • If the material gets thinner the opposite happens
• The machine makes adjustments to keep the thickness of the material constant

Uses of radiation: monitoring material thickness

Beta particles can be used to measure the thickness of thin materials such as paper, cardboard or aluminium foil

Diagnosis and treatment of cancer using gamma rays

• Radiotherapy is the name given to the treatment of cancer using radiation
  • Chemotherapy is treatment using chemicals
• Radiation can kill living cells
  • Some cells, such as bacteria and cancer cells, are more susceptible to radiation than others
• Beams of gamma rays are directed at the cancerous tumour
  • Gamma rays are used because they can penetrate the body, reaching the tumour
  • The beams are moved around to minimise harm to healthy tissue whilst still being aimed at the tumour

Uses of gamma radiation: treatment of cancer

Radiation therapy to remove a tumour

• A tracer is a radioactive isotope that can be used to track the movement of substances, like blood, around the body
  • A PET scan can detect the emissions from a tracer to diagnose cancer and determine the location of a tumour