A surgeon uses gamma rays to treat a patient's tumour. A security officer at an airport uses X-rays to scan luggage. Explain why both gamma rays and X-rays are able to cause harm to living cells, and state one use of microwaves, including the specific hazard microwaves pose to the human body.

Edexcel GCSE Physics (1PH0) — 5.1 Light and the electromagnetic spectrum · Explain · 4 marks · View as Markdown

Written & reviewed by James Millett — Biology (Imperial College London), PGCE Science (University of Cambridge).

Model answer (4 marks)

Gamma rays and X‑rays have very high frequencies, giving them high photon energy.
The high energy can ionise atoms in living cells, damaging DNA and causing mutations or cancer.
Microwaves are used for cooking food.
Microwaves cause internal heating of body cells by exciting water molecules, which can lead to burns if exposed to high power.

Examiner tips

  • Use the term ‘high frequency’ and ‘high energy’ for the first two points. Mention ionisation and DNA damage for the harm. Give a specific microwave use (e.g. cooking) and state the heating hazard. Keep each point short and to the point.

Common mistakes

  • Confusing ‘high frequency’ with ‘high wavelength’. Failing to mention ionisation or DNA damage. Giving a microwave use that is not recognised (e.g. radio broadcasting). Omitting the heating hazard or describing it vaguely.

Mark scheme (4 marks)

  1. Gamma rays and X-rays have high frequency (and therefore high energy)
  2. This high energy causes mutation or damage to cells / can cause cancer
  3. A correct use of microwaves stated (e.g. cooking food / satellite communications)
  4. Microwaves cause internal heating of body cells

Key terms in this question

gamma rays · X-rays · microwaves

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