A scientist is working with a radioactive source that emits beta radiation. Describe what beta radiation is and explain why a thin sheet of aluminium is able to stop beta radiation but would not stop gamma radiation.

Eduqas GCSE Physics — 9.2 Absorption and emission of ionising radiations · Describe and Explain · 4 marks · View as Markdown

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

Model answer (4 marks)

Beta radiation consists of fast‑moving electrons emitted from the nucleus. Beta particles are light and have a small mass, so a few millimetres of aluminium can absorb them. Gamma radiation is a high‑energy electromagnetic wave; it has no mass or charge and is highly penetrating. Aluminium is not dense or thick enough to stop gamma rays, which require thick lead or concrete for significant absorption.

Examiner tips

  • Use the word "beta radiation" and state it is electrons; mention aluminium thickness; contrast with gamma’s lack of mass and need for heavy shielding.
  • Show clear comparison: light vs. heavy, small vs. large penetration.

Mark scheme (4 marks)

  1. Beta radiation consists of fast-moving electrons (emitted from the nucleus)
  2. Beta particles have a small mass / are relatively light particles, so they can be absorbed by a few millimetres of aluminium
  3. Gamma radiation is a high-energy electromagnetic wave / has no mass and no charge
  4. Gamma radiation is very penetrating and requires thick lead or thick concrete to be significantly absorbed / aluminium is not thick or dense enough to stop gamma

Key terms in this question

beta radiation · gamma radiation

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