Knowledge Organiser: Uses and Hazards of Radiation
Key Terms
- Irradiation: External exposure to radiation
- Contamination: Radioactive material on/in body
- Tracer: Gamma source used to image organs
- Radiotherapy: Gamma rays to kill cancer
Radiation and Uses
- Alpha → smoke detectors
- Beta → paper thickness control
- Gamma → checking welds, medical tracers, radiotherapy, sterilisation
Safety: 3Ds
- Distance — stay further away
- Duration — reduce exposure time
- Dense shielding — use lead/concrete
- Tongs, not hands; badges to monitor
Exam Tips
- Justify radiation choice with properties
- Medical tracers: short half-life + gamma
- Contamination is more dangerous than irradiation
- Sterilised food is NOT radioactive
Key Equations
- Activity (Bq) = decays per second — higher activity = more radiation emitted
- Dose (Sv/mSv) measures biological effect of radiation on the body
- Distance reduces radiation intensity: the further you are from the source, the less radiation reaches you
- Absorbed dose (Gray, Gy) = energy deposited per kg of tissue
Common Mistakes
- Confusing contamination and irradiation: Irradiation is exposure to radiation from an external source (stops when source is removed); contamination means radioactive material enters/touches the body (continues to irradiate from inside/on skin)
- Saying irradiated food becomes radioactive: Food irradiated with gamma rays to kill bacteria does not become radioactive — it is safe to eat
- Choosing the wrong radiation type for an application: Medical tracers need gamma (penetrates tissue to be detected outside) with short half-life; cancer treatment uses gamma targeted at the tumour; smoke detectors use alpha (ionises air between plates)
- Not justifying radiation choice with properties: Always explain WHY a particular radiation is chosen — link to penetration, ionising power, half-life, and safety in context
- Forgetting lead/concrete for gamma shielding: Alpha is stopped by paper/skin; beta by thin aluminium; gamma requires thick lead or concrete — use the correct shielding material for each type
Memory Aid
- Smoke detectors — need to stay INSIDE the detector → short-range → Alpha
- Paper thickness — need to partially go through paper → Medium penetration → Beta
- Checking welds — need to go through thick metal → Maximum penetration → Gamma
- Medical tracers — need to escape the body to be detected → Gamma