Fiducia TogetherRadioactivity
Unstable nuclei, three kinds of radiation, and half-life.
Please note: This page explains a word or a process in education. It is general information about the system, the law and the guidance in England — not advice about your child, your school or your exam. If a decision is going against you, get advice from one of the free services we link to before you agree to anything or miss a deadline. If you are revising, check your own exam board's specification: boards word things differently and yours is the one that marks you.
What it is
Radioactive decay is the random emission of radiation from an unstable nucleus. Alpha is a helium nucleus, stopped by paper; beta is a fast electron, stopped by aluminium; gamma is electromagnetic radiation, reduced by lead.
Where it applies
GCSE physics and combined science.
How it works
Half-life is the time for half the undecayed nuclei to decay, or for the count rate to halve. Decay is random — you cannot predict which nucleus, only the behaviour of large numbers.
Irradiation is being exposed to radiation; contamination is having radioactive material on or in you. They are examined as a pair.
How to use it in your work
Half-life questions: halve repeatedly and count the halvings. Show each step.
Irradiation versus contamination comes up almost every year — learn one sentence distinguishing them.
Say decay is random and cannot be predicted for an individual nucleus. That is a mark.
Where to get help
Your teacher, your board's specification for the depth required at your tier, and Bitesize for the diagrams. The subject song runs the topics in order.
Revise this with a song
These are ours. We write revision songs because a lot of people remember a tune when they cannot remember a page, and because revising out loud in the kitchen beats staring at a highlighter.
- The Physics Song The GCSE physics specification, set to music.
Where to read more
Last reviewed 2026-08-28 by Fiducia Together · Next review due 2027-08-28
Please note: This page explains a word or a process in education. It is general information about the system, the law and the guidance in England — not advice about your child, your school or your exam. If a decision is going against you, get advice from one of the free services we link to before you agree to anything or miss a deadline. If you are revising, check your own exam board's specification: boards word things differently and yours is the one that marks you.