A doctor uses gamma rays to treat a patient's cancer. After the treatment, the patient asks why gamma rays were chosen instead of radio waves to target and destroy the cancer cells. Explain why gamma rays are more suitable than radio waves for destroying cancer cells, and describe one risk to healthy cells from using gamma rays.
Written & reviewed by James Millett — Biology (Imperial College London), PGCE Science (University of Cambridge).
Gamma rays and radio waves are both part of the electromagnetic spectrum. Gamma rays have the highest frequency in the electromagnetic spectrum, whilst radio waves have the lowest.
Model answer (5 marks)
Gamma rays have a higher frequency than radio waves.
Because frequency is higher, each gamma‑ray photon carries more energy (E=hf). The greater energy can break chemical bonds and damage the DNA of cancer cells, leading to cell death.
Radio waves have a much lower frequency and therefore much lower photon energy; they cannot damage or destroy cells and would be ineffective for treatment.
A risk of using gamma rays is that the high‑energy photons can also damage healthy cells in the surrounding tissue, potentially causing mutations that may lead to secondary cancers.
Because frequency is higher, each gamma‑ray photon carries more energy (E=hf). The greater energy can break chemical bonds and damage the DNA of cancer cells, leading to cell death.
Radio waves have a much lower frequency and therefore much lower photon energy; they cannot damage or destroy cells and would be ineffective for treatment.
A risk of using gamma rays is that the high‑energy photons can also damage healthy cells in the surrounding tissue, potentially causing mutations that may lead to secondary cancers.
Examiner tips
- State the frequency difference first, then link to photon energy, then to cell damage; finish with a clear risk statement.
- Use the exact terminology: ‘higher frequency’, ‘photon energy’, ‘DNA damage’, ‘secondary cancer’.
- Keep the answer concise – 5 marks can be earned with 4–5 short sentences.
Common mistakes
- Confusing radio waves with X‑rays or microwaves; not recognising that radio waves lack sufficient energy.
- Failing to mention the risk to healthy cells or describing it vaguely.
- Using non‑examiner terminology such as ‘high‑energy radiation’ without linking to photon energy.
Mark scheme (5 marks)
- Gamma rays have a higher frequency than radio waves
- Higher frequency means gamma rays carry more energy (per wave/photon)
- The greater energy of gamma rays can cause mutations or damage to cancer cells / sufficient energy to destroy cancer cells
- Radio waves do not carry enough energy to damage or destroy cells (so would be ineffective)
- Gamma rays can cause mutation or damage to healthy/surrounding cells, which could cause cancer in those cells
Key terms in this question
Related
- All Edexcel A-Level Physics (9PH0) revision notes →
- How to answer a "Explain" question →
- Decode the mark scheme abbreviations →
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