Gamma radiation is described as electromagnetic radiation, whilst alpha and beta radiations are described as particles. Explain what is meant by the term 'ionising radiation' and describe how alpha particles cause ionisation as they travel through air.

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

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

Model answer (4 marks)

Ionising radiation is radiation that can remove electrons from atoms, creating ions.
Alpha particles are positively charged (+2). As they travel through air, their charge attracts electrons in surrounding atoms, pulling them away and ionising the atoms.
Because of their large charge and mass, alpha particles interact frequently with matter, losing energy rapidly and therefore are strongly ionising, giving them a short range in air.

Examiner tips

  • Define ionising radiation as electron‑removing. Mention alpha’s +2 charge. Explain attraction of electrons. Highlight high interaction rate and short range.

Common mistakes

  • Confusing ionising with non‑ionising. Forgetting to state the +2 charge. Saying alpha particles are weakly ionising instead of strongly.

Mark scheme (4 marks)

  1. Ionising radiation is radiation that can remove electrons from atoms (creating ions)
  2. Alpha particles are positively charged (carry a charge of +2)
  3. The charge on the alpha particle attracts / interacts with electrons in surrounding atoms
  4. Alpha particles are strongly ionising because they interact frequently / have a short range in air, losing energy rapidly

Key terms in this question

ionising radiation · alpha particle · ionisation

Related

More Types of radiation questions

▶ Try answering this question with AI marking (free) →