A student is investigating three types of nuclear radiation: alpha, beta and gamma. Describe how the penetrating ability of each type of radiation differs, and state what material is needed to stop each type.

WJEC GCSE Physics (Wales) — 2.7 Types of radiation · Describe · 4 marks · View as Markdown

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

Model answer (4 marks)

Alpha radiation has the least penetrating ability – it can be stopped by a few centimetres of air or a sheet of paper.
Beta radiation has intermediate penetrating ability – it is stopped by a few millimetres of aluminium (or an equivalent thin metal sheet).
Gamma radiation has the greatest penetrating ability – it is not completely stopped but is significantly reduced by thick lead or thick concrete.
Thus the order of penetration is: alpha < beta < gamma.

Examiner tips

  • Use the exact wording for materials (paper, aluminium, lead, concrete).
  • Show the correct order of penetration explicitly.
  • Mention that gamma is not completely stopped but reduced.

Common mistakes

  • Confusing the order of penetration (alpha > beta).
  • Using the wrong material for beta (e.g. plastic instead of aluminium).
  • Saying gamma can be completely stopped by lead.

Mark scheme (4 marks)

  1. Alpha radiation has the least penetrating ability / is stopped by a few centimetres of air or a sheet of paper
  2. Beta radiation has intermediate penetrating ability / is stopped by a few millimetres of aluminium (or equivalent thin metal sheet)
  3. Gamma radiation has the greatest penetrating ability / is never completely stopped but is significantly reduced by thick lead or thick concrete
  4. Correct ordering of penetrating ability: alpha least, beta intermediate, gamma greatest

Key terms in this question

penetrating ability

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