A hospital uses a radioactive source to treat a tumour inside a patient's body. The source emits gamma radiation and has a long half-life. Explain why gamma radiation and a long half-life are both suitable properties for this medical use.
Written & reviewed by James Millett — Biology (Imperial College London), PGCE Science (University of Cambridge).
Model answer (4 marks)
Gamma radiation is highly penetrating, so it can pass through body tissue to reach the tumour inside the patient
Alpha and beta radiation would be absorbed by surrounding tissue before reaching the tumour, so only gamma is suitable
A long half‑life means the source remains active and does not decay significantly during the course of treatment
A long half‑life means the dose delivered to the patient is consistent and predictable over the treatment period
Alpha and beta radiation would be absorbed by surrounding tissue before reaching the tumour, so only gamma is suitable
A long half‑life means the source remains active and does not decay significantly during the course of treatment
A long half‑life means the dose delivered to the patient is consistent and predictable over the treatment period
Examiner tips
- Use the word ‘penetrating’ to show understanding of gamma radiation’s properties
- Explain why alpha and beta are unsuitable by mentioning absorption in tissue
- Show that a long half‑life keeps the activity stable during treatment
- Link the stable dose to predictable treatment outcomes
Common mistakes
- Confusing gamma with alpha or beta radiation as the suitable type
- Forgetting to mention the stability of dose over time
- Using vague terms like ‘strong’ instead of ‘penetrating’
Mark scheme (4 marks)
- Gamma radiation is highly penetrating, so it can pass through body tissue to reach the tumour inside the patient
- Alpha and beta radiation would be absorbed by surrounding tissue before reaching the tumour, so only gamma is suitable
- A long half-life means the source remains active / does not decay significantly during the course of treatment
- A long half-life means the dose delivered to the patient is consistent / predictable over the treatment period
Key terms in this question
gamma radiation · half-life · radioactive source
Related
- All Eduqas GCSE Physics revision notes →
- How to answer a "Explain" question →
- Decode the mark scheme abbreviations →
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