Radioactive Contamination
Master Radioactive Contamination for GCSE Physics with this free worksheet and full mark scheme — Foundation and Higher exam-style questions with worked answers for AQA, Edexcel and OCR. Irradiation is exposure to radiation, while contamination is the unwanted presence of radioactive atoms on or in an object.
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These worksheets and mark schemes are original, written for Virtus Academy and checked against the current AQA, Edexcel and OCR specifications. Every worksheet comes with a full mark scheme.
Topic overview
Radioactive contamination and irradiation are different things, and confusing them is the most common error in this topic.
Contamination is the unwanted presence of materials containing radioactive atoms on or in other materials. The hazard comes from the decay of the contaminating atoms, and it continues as long as the contaminating material is present.
Irradiation is the process of exposing an object to nuclear radiation. The object does not become radioactive as a result. Suitable precautions protect against irradiation — shielding, keeping a distance, and limiting exposure time. Studies on the effects of radiation are published and peer reviewed so findings can be checked by other scientists.
Revision notes
Contamination
Contamination is the unwanted presence of materials containing radioactive atoms on or in other materials.
The hazard comes from the decay of those atoms, and it continues for as long as the contaminating material remains. Removing the material removes the hazard.
Irradiation
Irradiation is the process of exposing an object to nuclear radiation.
The object does not become radioactive as a result. Once the source is removed or shielded, the irradiation stops immediately.
Precautions and peer review
Protection against irradiation: use shielding such as lead, keep as far from the source as possible, and limit the exposure time.
The published studies on the effects of radiation on humans are peer reviewed, so other scientists can check the findings and the conclusions can be trusted.
Key points
- Contamination is radioactive atoms on or in a material.
- Contamination continues while the material is present.
- Irradiation is exposure to nuclear radiation.
- An irradiated object does not become radioactive.
- Shielding, distance and time reduce irradiation.
- Studies are peer reviewed so findings can be checked.
Worked examples
Example 1
Explain the difference between contamination and irradiation. [3 marks]
Model answer
Contamination is the unwanted presence of materials containing radioactive atoms on or in an object (1 mark). Irradiation is the process of exposing an object to nuclear radiation (1 mark). An irradiated object does not itself become radioactive, whereas a contaminated one remains hazardous while the material is present (1 mark).
Example 2
Give three precautions that reduce the risk from irradiation. [3 marks]
Model answer
Use shielding such as lead between the source and the person (1 mark). Keep as far away from the source as possible (1 mark). Limit the time spent near the source (1 mark).
Example 3
Explain why studies on the effects of radiation are peer reviewed. [2 marks]
Model answer
Peer review allows other scientists to check the findings and the methods used (1 mark), so that the conclusions can be trusted and errors identified (1 mark).
Common mistakes
Saying an irradiated object becomes radioactive.
It does not — the radiation passes through it.
Using the two terms interchangeably.
Contamination involves radioactive material being present; irradiation is exposure.
Giving only one precaution.
Shielding, distance and time are all examinable.
Forgetting peer review.
It is specifically required by the specification.
Exam tips
- Learn the two definitions as a contrasting pair.
- State that irradiated objects do not become radioactive.
- Give all three precautions when asked.
- Mention peer review when discussing radiation studies.
Key terms
- Contamination
- Unwanted radioactive atoms on or in a material.
- Irradiation
- Exposure of an object to nuclear radiation.
- Shielding
- Material such as lead placed between source and person.
- Peer review
- Checking of scientific findings by other scientists.
Related topics
Written and reviewed against the current AQA, Edexcel and OCR specifications. Spotted an error? Let us know.