Pearson Edexcel International GCSE Physics · specification 4PH1 · Paper 1 | Whole paper: Core content, all eight topics · Free · no account needed
7(b) Radioactivity (4PH1 specification)
Unstable nuclei, the three emissions, and the half-life that makes decay predictable in bulk and random in detail.
Learn it on Incandio
The 5 Incandio pages that teach this — each explained in full, then proved in marked questions, taught back to an AI pupil and defended in a debate. Completely free.
- Alpha, Beta and Gamma — Three emissions from unstable nuclei, arriving at random — and why the one that is easiest to stop is the one to be most careful with.
- Nuclear Equations — What each kind of decay does to the numbers — and why losing a negative particle makes the charge go up.
- Detecting Radiation and Background — How you measure something invisible, and why the counter clicks even with no source in the room.
- Half-Life — Half of what is left, every time — which is why a radioactive sample never quite runs out.
- Uses and Dangers of Radiation — Choosing a source by its half-life and its penetration — and the difference between being irradiated and being contaminated.
The teaching route this belongs to: Topic 7 · Radioactivity and particles (Physics) — the lessons in order, with every gate.
Specification coverage
Topic 7 Radioactivity and particles (b) Radioactivity — statements 7.4–7.15
Assessment objectives: AO1, AO2. Suggested learning time: 70 minutes.
Required knowledge
- The structure of the atom and the meaning of atomic number, mass number and isotope
- The nature of alpha, beta and gamma radiation, their penetrating power and ionising ability
- Nuclear equations for alpha and beta decay
- Background radiation and its sources
- Half-life, and how to determine it from a graph or a table of data
- The dangers of ionising radiation and how exposure is reduced
Required skills
- Balance a nuclear equation for mass number and atomic number
- Determine half-life from decay data
- Select a suitable isotope for a use, and justify it by half-life and radiation type
How it is examined
- Multiple-choice and short-answer recall
- Calculations using the specification's relationships
- Extended open-response applying the physics to an unfamiliar situation
Common mistakes
- Treating decay as predictable for a single nucleus. Decay is random; half-life is a statistical property of a large sample.
- Forgetting that background radiation must be subtracted from a count rate before calculating half-life.
- Mixing up penetration and ionisation: alpha is the most ionising and the least penetrating.
This page maps the specification. The pages above teach it, and the Physics lessons hold the whole course — completely free.