A mobile phone uses microwaves to send and receive signals. Explain why engineers designing a new phone are advised to limit the intensity of microwaves that pass through a user's head.

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).

Mobile phones communicate via microwaves, which are part of the electromagnetic spectrum. Regulatory bodies set maximum limits on the power of microwaves that electronic devices are permitted to emit close to the human body.

Model answer (4 marks)

Microwaves are absorbed by body cells and tissues.

The absorbed energy is converted into heat, causing internal heating of the cells.

Higher intensity microwaves transfer more energy to the cells, increasing the temperature rise.

Excessive heating can damage cells and tissues, potentially harming the user.

Examiner tips

  • Use the exact terms 'absorbed', 'internal heating', 'higher intensity', 'damage cells' as in the mark scheme.
  • Show the causal chain: absorption → heating → damage.
  • Keep each point concise and separate.
  • Avoid unnecessary explanation or repetition.

Common mistakes

  • Using vague terms like 'radiation' instead of 'microwaves' or 'heat' instead of 'internal heating'.
  • Failing to mention the link between intensity and energy transfer.
  • Over‑expanding the answer with unrelated details.

Mark scheme (4 marks)

  1. Microwaves are absorbed by body cells / tissue
  2. This absorption causes internal heating of body cells
  3. Higher intensity means more energy is transferred to the cells
  4. This can damage body cells / cause harm to the user

Key terms in this question

microwaves · intensity

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