A technician is storing radioactive sources in a laboratory. One source emits alpha radiation, one emits beta radiation, and one emits gamma radiation. Describe the nature of each type of radiation and explain which source poses the greatest risk to a worker who accidentally swallows a source.

AQA A-Level Physics (7408) — 3.8.1 Radioactivity · Describe and Explain · 5 marks · View as Markdown

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

Model answer (5 marks)

Alpha radiation consists of a helium nucleus (two protons and two neutrons).
Beta radiation is a fast‑moving electron emitted from the nucleus.
Gamma radiation is electromagnetic radiation – a wave, not a particle.
The alpha source poses the greatest risk if swallowed.
Alpha particles are highly ionising and cannot escape the body, so they deposit all their energy in surrounding tissue, causing severe damage.

Examiner tips

  • Use the exact terminology (helium nucleus, fast‑moving electron, electromagnetic wave).
  • State clearly that alpha is the most ionising and cannot escape the body.
  • Mention the source that poses the greatest risk.

Common mistakes

  • Calling beta radiation a positron or confusing it with alpha.
  • Saying gamma is a particle instead of a wave.

Mark scheme (5 marks)

  1. Alpha radiation consists of a helium nucleus (two protons and two neutrons)
  2. Beta radiation is a fast-moving electron (emitted from the nucleus)
  3. Gamma radiation is electromagnetic radiation / a wave (not a particle)
  4. The alpha source poses the greatest risk when swallowed / inside the body
  5. Because alpha radiation is the most ionising / causes the most ionisation of body tissue, and cannot escape the body (is absorbed by surrounding tissue)

Key terms in this question

alpha radiation · beta radiation · gamma radiation

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