Electromagnetic waves transfer energy from a source to an absorber. Describe the properties that all electromagnetic waves share, and explain how infrared radiation and X-rays differ in their uses and hazards to the human body.
Written & reviewed by James Millett — Biology (Imperial College London), PGCE Science (University of Cambridge).
Model answer (5 marks)
All electromagnetic waves are transverse waves.
All electromagnetic waves travel at the same speed in a vacuum (3 × 10⁸ m/s).
Infrared radiation is used for cooking food, thermal imaging or short‑range communications.
Infrared radiation can cause skin burns.
X‑rays are used for medical imaging or security scanners and can cause cell damage or mutations.
All electromagnetic waves travel at the same speed in a vacuum (3 × 10⁸ m/s).
Infrared radiation is used for cooking food, thermal imaging or short‑range communications.
Infrared radiation can cause skin burns.
X‑rays are used for medical imaging or security scanners and can cause cell damage or mutations.
Examiner tips
- Use the exact terms ‘transverse waves’ and ‘3 × 10⁸ m/s’. Give one valid use for infrared and one for X‑rays. Mention a specific hazard for each type of radiation.
- Keep the answer concise – no extra sentences or explanations beyond the required points.
Common mistakes
- Writing ‘electromagnetic waves are longitudinal’. Forgetting to state the speed of light. Giving a use for infrared that is not recognised (e.g. ‘heating’ without context).
Mark scheme (5 marks)
- All electromagnetic waves are transverse waves
- All electromagnetic waves travel at the same speed in a vacuum (3 × 10⁸ m/s)
- Infrared radiation is used for cooking food, thermal imaging or short-range communications (any one valid use)
- Infrared radiation can cause skin burns (hazard to human body)
- X-rays are used for medical imaging or security scanners AND can cause cell damage or mutations
Key terms in this question
electromagnetic waves · infrared radiation · X-rays
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