A scientist uses three different types of electromagnetic radiation in a single day: microwaves to heat food, visible light to read a document, and X-rays to image a broken bone. Place these three types of radiation in order of increasing frequency, then explain how the frequency of X-rays compares to that of visible light.

Eduqas GCSE Physics — 6.1 Frequency range of the 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)

Microwaves, visible light, X‑rays

X‑rays have a higher frequency than visible light. All electromagnetic waves travel at the same speed, so a higher frequency means a shorter wavelength for X‑rays compared with visible light. Consequently, X‑rays carry more energy per photon than visible light.

Examiner tips

  • State the order clearly; use commas or a list. Mention that frequency increases from microwaves to visible light to X‑rays. Explain the speed–frequency–wavelength relationship. Note the energy–frequency link to justify why X‑rays are more energetic.

Common mistakes

  • Mixing up the order (e.g. putting X‑rays before visible light). Forgetting to mention that all EM waves travel at the same speed. Failing to connect higher frequency with shorter wavelength and higher photon energy.

Mark scheme (4 marks)

  1. Correct order: microwaves, then visible light, then X-rays (increasing frequency)
  2. X-rays have a higher frequency than visible light
  3. All electromagnetic waves travel at the same speed (in a vacuum / in air), so a higher frequency means a shorter wavelength for X-rays compared to visible light
  4. X-rays carry more energy per photon than visible light because energy increases with frequency

Key terms in this question

frequency · X-rays · visible light · microwaves

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