Hazards and uses of radioactivity
Ionising radiation (alpha, beta, gamma) damages living cells by stripping electrons from atoms in DNA, proteins and water. Damaged cells may die or, worse, become cancerous.
Irradiation vs contamination
| Term | Meaning | Stops when... |
|---|---|---|
| Irradiation | Being exposed to radiation from an outside source | Source is removed or shielded |
| Contamination | Radioactive material is on or inside you | Material is washed off / decays / removed |
Contamination is usually more dangerous because the source remains in contact with tissue.
Hazards by radiation type
| Type | Outside the body | Inside the body |
|---|---|---|
| Alpha | Stopped by skin — low risk | Very dangerous: highly ionising, all energy deposited locally |
| Beta | Penetrates skin — moderate risk | Less ionising than alpha but penetrates further |
| Gamma | Penetrates deeply — moderate risk | Less ionising but reaches all organs |
Safety measures
- Shielding (lead aprons, concrete walls).
- Distance (use long tongs).
- Time (limit exposure).
- PPE (gloves, masks for contamination).
- Monitor exposure with a film badge or dosimeter.
Uses of radioactivity
| Use | Source | How it works |
|---|---|---|
| Medical imaging (PET, gamma camera) | Technetium-99m (gamma) | Tracer follows blood to organs; gamma escapes for imaging |
| Cancer treatment (radiotherapy) | Cobalt-60 (gamma) | High doses kill cancer cells; rotate beam to spare healthy tissue |
| Sterilisation of medical instruments | Gamma | Penetrates packaging, kills microbes |
| Smoke detector | Americium-241 (alpha) | Smoke disrupts ionised air gap, alarm sounds |
| Industrial thickness control | Beta | Detector measures intensity through paper/foil |
| Carbon dating | Carbon-14 (beta) | Decay rate compared to atmospheric ratio |
Why pick each isotope? Half-life (long enough to be useful, short enough to leave the body), penetrating power (gamma for imaging, alpha for trapped sources), and how strongly it ionises.
WJEC exam tip
For "compare irradiation and contamination", the punchline is "irradiation stops when the source is removed; contamination keeps exposing you." Memorise this single sentence and you'll usually get both marks.
AI-generated · claude-opus-4-7 · v3-wjec-combined-science-leaves