Irradiation vs Contamination: what's the difference?
GCSE Physics
Both involve radioactive sources, but they are examined as opposites — the key is whether the radioactive material itself ends up on/in the object.
Written & reviewed by James Millett — Biology (Imperial College London), PGCE Science (University of Cambridge).
Irradiation vs Contamination — side by side
| Irradiation | Contamination | |
|---|---|---|
| What it is | Exposing an object to radiation from an outside source | Getting radioactive atoms onto or into an object |
| Is the object radioactive afterwards? | No — it does not become radioactive | Yes — it now contains a radioactive source |
| When does the exposure stop? | Stops the moment the source is removed | Continues — the source stays with the object |
| How to protect against it | Shielding, distance, limiting time | Gloves, protective clothing, keeping sources sealed |
Exam tip — how to tell them apart: Ask yourself: "Is the radioactive material actually ON the object?" If yes → contamination. If it is just being exposed to rays from a distance → irradiation.
Common trap: Students often say irradiation makes an object radioactive — it does not. Only contamination leaves radioactive atoms behind.
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