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Leaving Cert Physics: Radioactivity

How often Radioactivity comes up on the Physics papers, every year it was asked, and questions to try.

HL Asked on 10 of the last 10 Higher Level papers, most recently in 2026. banker

OL Asked on 9 of the last 10 Ordinary Level papers, most recently in 2025. banker

June 2027 is the first exam on the new Physics course. These come from the 2016–2026 papers, so read them as a guide.

Radioactivity, Higher Level(6 marks)

Quick ones on Radioactivity.

(a)Which type of radiation is stopped by a sheet of paper?
  1. Beta
  2. Alpha
  3. Gamma
(b)Unit of activity of a radioactive source?
  1. Coulomb (C)
  2. Gray (Gy)
  3. Becquerel (Bq)
(c)What is an alpha particle?
  1. A helium nucleus, two protons and two neutrons
  2. A high-energy photon given out by a nucleus
  3. A fast-moving electron given out by an unstable nucleus
Show the answers

(a) Alpha

(b) Becquerel (Bq)

(c) A helium nucleus, two protons and two neutrons

Your turn: Higher Level questions on Radioactivity.

Higher Level

Asked on 10 of the last 10 Higher Level papers, most recently in 2026. banker

Every paper, year by year

YearWhere it came up
2026Q12
2025Q14(c)
2024Q10, Q14(b)
2023Q9
2022Q10, Q11
2021Q6(k), Q11
2019Q5(h), Q5(i)
2018Q12(b)
2017Q12(b)
2016Q9, Q12(a)

Links open the State Examinations Commission’s paper for that year.

More Radioactivity questions

Radioactivity, 3 marks

Why do large stable nuclei have more neutrons than protons?

  1. Neutrons are lighter than protons, so they make the nucleus less heavy
  2. Protons attract each other electrically, so neutrons are needed to keep them apart
  3. Extra neutrons add strong-force attraction without adding electrical repulsion
Show the answer

Extra neutrons add strong-force attraction without adding electrical repulsion

Protons repel each other. Neutrons feel the short-range strong force but have no charge, so extra neutrons help hold a big nucleus together.

Radioactivity, 3 marks

Which radiation is deflected most by an electric field?

  1. Gamma rays
  2. Beta particles
  3. Alpha particles
Show the answer

Beta particles

Beta particles are about 7000 times lighter than alpha particles, so they bend far more (and the opposite way). Gamma rays carry no charge and are not deflected.

Radioactivity, 2 marks

Which type of radiation is the most strongly ionising?

  1. Alpha
  2. Gamma
  3. Beta
Show the answer

Alpha

Alpha particles are big, slow and doubly charged, so they knock electrons off many atoms in a short distance. That is also why a few cm of air or a sheet of paper stops them.

Ordinary Level

Asked on 9 of the last 10 Ordinary Level papers, most recently in 2025. banker

Every paper, year by year

YearWhere it came up
2026Not asked
2025Q12
2024Q6(i), Q12
2023Q13
2022Q6(l), Q14(d)
2021Q12
2019Q5(j), Q12(d)
2018Q5(i)
2017Q5(j), Q10
2016Q5(j)

Links open the State Examinations Commission’s paper for that year.

More Radioactivity questions

Radioactivity, 2 marks

What is a beta particle?

  1. A helium nucleus of two protons and two neutrons
  2. A high-energy photon of electromagnetic radiation
  3. A fast-moving electron from the nucleus
Show the answer

A fast-moving electron from the nucleus

Beta particles are electrons given out by the nucleus. A helium nucleus is an alpha particle; a high-energy photon is gamma.

Radioactivity, 3 marks

A nucleus gives out an alpha particle. Its mass number?

  1. Stays the same
  2. Decreases by 4
  3. Decreases by 2
Show the answer

Decreases by 4

An alpha particle is 2 protons + 2 neutrons, so the mass number falls by 4 and the atomic number falls by 2.

Radioactivity, 2 marks

Which type of radiation is the most penetrating?

  1. Gamma
  2. Alpha
  3. Beta
Show the answer

Gamma

Alpha is stopped by paper and beta by a few mm of aluminium. Gamma needs thick lead or concrete to reduce it.

Other Physics topics

All of Leaving Cert Physics