Gamma radiation, alpha particles and beta particles are all types of nuclear radiation. Compare the penetrating power and ionising ability of gamma radiation and alpha particles, and explain how these properties are linked.

WJEC GCSE Physics (Wales) — 2.4 The atom, the nucleus and radioactivity · Compare · 4 marks · View as Markdown

Written & reviewed by James Millett — Biology (Imperial College London), PGCE Science (University of Cambridge).

Model answer (4 marks)

Gamma radiation has a much greater penetrating power than alpha particles – it can pass through several centimetres of lead, whereas alpha particles are stopped by a few centimetres of air or a sheet of paper.
Alpha particles have a much greater ionising ability than gamma radiation.
Because alpha particles interact strongly with surrounding matter, they lose their energy rapidly and therefore do not penetrate far.
Because gamma radiation interacts weakly with matter, it loses energy slowly and consequently has high penetrating power.

Examiner tips

  • Use the word ‘greater’ to compare penetrating power and ionising ability. Mention specific examples (lead, paper, air) to show understanding. Explain the link between interaction strength, energy loss and penetration.
  • common_mistakes
  • :
  • Confusing the order of magnitude of penetration (e.g. saying alpha penetrates more than gamma). Forgetting to mention the ionising ability difference. Using vague phrases like ‘stronger’ without specifying which property is greater.

Mark scheme (4 marks)

  1. Gamma radiation has greater penetrating power than alpha particles (e.g. gamma can penetrate several centimetres of lead / alpha is stopped by a few centimetres of air or a sheet of paper)
  2. Alpha particles have greater ionising ability than gamma radiation
  3. Because alpha particles interact strongly with surrounding matter (causing ionisation), they lose their energy quickly and so do not penetrate far
  4. Because gamma radiation interacts weakly with matter (low ionising ability), it does not lose energy quickly and therefore has high penetrating power

Key terms in this question

penetrating power · ionising ability · gamma radiation · alpha particles · nuclear radiation

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