Cambridge IGCSE Physics Notes 5.2: Radioactivity
Cambridge IGCSE Physics radioactivity notes on detection, alpha, beta, gamma, decay, equations, half-life, background radiation, uses, and safety.
Q: What does Cambridge IGCSE Physics Notes 5.2: Radioactivity cover?
A: It follows official Cambridge Physics section 5.2 for syllabuses 0625 and 0972, with Core ideas separated from Supplement depth.
Radioactive decay is random for one nucleus but predictable for a large sample, allowing activity and half-life to be analysed statistically.
The ideas that organise this section
- Alpha, beta, and gamma differ in nature, charge, ionising ability, and penetration.
- Half-life is the time for activity or undecayed nuclei to fall to half, independent of the starting amount.
- Safety reduces time, increases distance, and uses suitable shielding while controlling contamination.
Core route
Core candidates should be ready to describe, calculate, interpret, and apply the following:
- Describe detection, background radiation, emission properties, uses, and hazards.
- Complete simple nuclear equations and read half-life from tables or graphs.
- Apply practical safety precautions to source handling.
Supplement route
Extended candidates study all Core content and add the following depth:
- Explain random decay and use repeated halving quantitatively.
- Distinguish irradiation from contamination and match shielding to radiation type.
- Evaluate a radioactive source choice using penetration and half-life.
Formula route
- Relationship: remaining fraction after n half-lives = one half raised to n.
Write the relationship before substituting. Convert units first, keep extra figures during working, and round only the final answer to sensible precision.
Build a connected model
In Radioactivity, a strong answer connects the named quantity or model to observable evidence. Begin by defining the physical quantity in words or with its relationship. Identify which values are scalars and which require a direction. Represent the situation with a labelled diagram, graph, field pattern, ray or circuit when that makes the relationship visible. The representation is part of the reasoning: its labels, arrows and scale should agree with the written explanation.
For a calculation, write the governing relationship before substitution, convert prefixes and time units, keep unrounded values during working and attach the correct final unit. For a qualitative question, use a cause-link-consequence chain. Name what changes, state the physical mechanism that links the change to the system, and then give the measurable result. If two cases are compared, hold unrelated variables constant and use the same physical principle for both.
