IGCSE Physics: Atomic and Nuclear Physics

Nuclear physics is a gift to anyone who learns the definitions properly. The examiners recycle the same questions year after year: define half-life, compare α/β/γ, balance a nuclear equation, describe one real-world use of radiation. Know the script and this topic becomes free marks.

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What you need to master

1Structure of the atom, nucleons, atomic number Z, mass number A.
2Isotopes: same Z, different A, and examples.
3Alpha, beta (minus) and gamma radiation — nature, ionising and penetrating powers.
4Balanced nuclear equations for α and β decay.
5Half-life: definition, graph interpretation and calculations.
6Background radiation, sources and safety precautions.
7Uses of radioactivity: medical tracers, sterilisation, dating.

Key formulas

A = Z + N

After n half-lives: activity = initial / 2ⁿ

Examiner tips

•For half-life, say "the time taken for HALF the radioactive NUCLEI to decay" — not "half the atoms", not "half the sample".
•Always give the stopping material: alpha → paper, beta → few mm aluminium, gamma → thick lead / concrete.
•In nuclear equations check that mass number and atomic number both balance.

Common mistakes to avoid

•Treating half-life as a constant countdown rather than a statistical property.
•Forgetting that β⁻ decay turns a neutron into a proton, increasing Z by 1.
•Claiming gamma radiation has no effect on living tissue because it is "only waves".