A hospital uses different types of electromagnetic radiation for different medical purposes. Describe the properties of X-rays that make them suitable for producing images of bones inside the body, and explain why visible light cannot be used for the same purpose.
Written & reviewed by James Millett — Biology (Imperial College London), PGCE Science (University of Cambridge).
Electromagnetic radiation covers a wide spectrum of waves, from radio waves to gamma rays. Different parts of the spectrum have different properties and are used for different applications in medicine.
Model answer (4 marks)
X‑rays are high‑energy electromagnetic waves that can penetrate soft tissue such as skin and muscle, but are absorbed by denser materials like bone. The absorption creates a shadow on a detector, giving an image of the bones. Visible light has much lower energy and is absorbed or reflected by skin and tissue, so it cannot reach the bones to produce an internal image.
Examiner tips
- Use the words 'penetrate' and 'absorb' to link properties to imaging
- Explain the contrast between soft tissue and bone
- Mention the detector or film to show image formation
Common mistakes
- Confusing visible light with X‑rays as both being electromagnetic
- Saying visible light can penetrate tissue
- Not explaining why absorption leads to an image
Mark scheme (4 marks)
- X-rays can penetrate/pass through soft tissue (flesh/muscle)
- X-rays are absorbed by / cannot pass through bone (denser material), producing a shadow/image
- Visible light cannot penetrate/pass through skin or body tissue (is absorbed/reflected at the surface)
- Therefore visible light cannot reach the bones to produce an internal image
Key terms in this question
Related
- All OCR GCSE Physics A: Gateway Science (J249) revision notes →
- How to answer a "Describe" question →
- Decode the mark scheme abbreviations →