Explain why X-rays are used to produce images of bones inside the human body, but infrared radiation is not suitable for this purpose. Your answer should refer to the properties of both types of electromagnetic radiation.

Cambridge International IGCSE Physics (0625) — 3.3 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)

X‑rays have a very high frequency and short wavelength, so they can penetrate soft tissue but are absorbed by the dense bone, giving a clear image of the bone structure.
Infrared radiation has a low frequency and long wavelength; it is absorbed by soft tissue and cannot penetrate the body, so it cannot reach the bone to produce an image.

Examiner tips

  • Mention the high frequency/short wavelength of X‑rays and low frequency/long wavelength of infrared. Explain penetration vs absorption. Show the logical conclusion that infrared cannot image bone.

Common mistakes

  • Confusing which radiation penetrates soft tissue. Forgetting to state that infrared is absorbed by skin. Using vague terms like "strong" or "weak" instead of frequency/wavelength.

Mark scheme (4 marks)

  1. X-rays have a high frequency / short wavelength (compared to infrared)
  2. X-rays can penetrate soft tissue / pass through the body but are absorbed by / cannot pass through dense bone
  3. Infrared radiation is absorbed by / cannot penetrate soft tissue / skin
  4. Therefore infrared cannot reach the bone / produce an image of internal bone structure

Key terms in this question

X-rays · infrared

Related

More Electromagnetic spectrum questions

▶ Try answering this question with AI marking (free) →