Practical Applications of Radiation
Physics: Cambridge International GCSE Supplement, topic 5.4.5
Practical Applications of Radiation
Household fire (smoke) alarms
- Use alpha particles (commonly americium-241).
- A radioactive material fires alpha particles at a smoke detector.
- If there is smoke between the radioactive material and the smoke detector, then fewer alpha particles will reach the detector.
- This will set off the smoke alarm.
- The isotope must have a long half-life so the alarm works reliably for many years without needing replacement.
Irradiating food to kill bacteria
- Uses gamma rays, because they penetrate deeply into food and kill bacteria without making the food radioactive.
- The source needs a long half-life so it can be used for months/years without frequent replacement.
Sterilisation of equipment using gamma rays
We can use gamma radiation to sterilise medical equipment in hospitals.
Sterilisation kills bacteria and viruses.
Uses gamma radiation, as it penetrates packaging and kills microbes inside sealed equipment.
Requires a source with a long half-life to remain effective over long periods.
Measuring and controlling thickness of materials
Uses beta radiation.
Beta particles can penetrate thin materials like paper or metal foils, but are absorbed if the material is too thick.
The detector measures how much beta passes through and adjusts the thickness accordingly.
The source usually needs a reasonably long half-life for continuous industrial use.
Diagnosis and treatment of cancer using gamma rays
Diagnosis:
Short-lived gamma emitters (like technetium-99m) are used in medical tracers.
Gamma can escape the body and be detected, while the short half-life limits the patient’s radiation exposure.
Treatment:
Strong, long-lived gamma sources are used to target and kill cancer cells deep inside the body.
Test yourself on Practical Applications of Radiation
How does a smoke detector work?
Why are alpha emitters used in smoke alarms?
Why is a long half-life important for smoke alarm isotopes?
Which type of radiation is used to sterilise food?
Why must the gamma source have a long half-life?