A student states: 'All electromagnetic waves are dangerous to humans because they all carry energy.' Evaluate this statement.
Written & reviewed by James Millett — Biology (Imperial College London), PGCE Science (University of Cambridge).
Different types of electromagnetic waves have different frequencies and wavelengths. Higher frequency electromagnetic waves carry more energy per wave.
Model answer (5 marks)
All electromagnetic waves transfer energy from source to absorber, so the statement is partly correct. However, energy alone does not make a wave dangerous. Higher‑frequency waves such as UV, X‑rays and gamma rays carry more energy per photon and can ionise atoms, damaging DNA and causing mutations, skin cancer or eye damage. Infra‑red can cause skin burns and microwaves can heat body tissues. In contrast, lower‑frequency waves – radio, visible light and even some infrared – are generally harmless under normal exposure, so carrying energy does not automatically mean danger.
Examiner tips
- Show understanding of energy transfer and frequency dependence; give specific harmful examples; contrast with harmless waves; keep answer concise and use correct terminology.
- Use the word ‘evaluate’ to discuss both sides of the statement.
Mark scheme (5 marks)
- The student is partially correct — electromagnetic waves do all transfer energy from source to absorber
- However, the statement is not fully correct because not all electromagnetic waves are dangerous to humans
- Higher frequency electromagnetic waves (such as ultraviolet, X-rays, or gamma rays) carry more energy and can cause cell damage or mutations
- Named example of a specific danger linked correctly to a specific type of EM wave (e.g. ultraviolet causes skin cancer / eye damage; infrared causes skin burns; microwaves cause internal heating of body cells)
- Lower frequency / longer wavelength electromagnetic waves such as radio waves or visible light are not considered harmful under normal exposure conditions, so carrying energy alone does not make a wave dangerous
Key terms in this question
Related
- All Edexcel A-Level Physics (9PH0) revision notes →
- How to answer a "Evaluate" question →
- Decode the mark scheme abbreviations →
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