A-Level Physics: Radioactive Decay

Radioactivity at A2 upgrades the GCSE picture with exponential mathematics and quantitative nuclear structure — and its questions are among the most formulaic on the paper, which makes them highly trainable. This quiz covers the full examinable range.

The radiation-properties questions test the comparative physics precisely: why an alpha particle's far greater mass gives it a much larger radius of curvature than a beta particle in the same magnetic field, how the three radiation types behave in an electric field (alpha toward the negative plate, gamma undeflected), and which combinations of ionising power and penetration genuinely describe each type. The inverse square law for gamma radiation appears as a doubling-the-distance calculation.

The decay-mathematics questions work the exponential machinery: half-life reasoning for activity after three half-lives, the decay-constant route to the time for a sample to fall to 25% (two half-lives via ln 2 over λ), and the definitions question separating what the decay constant is — probability of decay per unit time — from what it is not. Activity units get their own question distinguishing the becquerel from its impostors.

Nuclear structure appears through the r = r₀A^⅓ relation: scaling a known nuclear radius from mass number 64 to 216, where the cube-root ratio gives a clean factor of 1.5 — the standard exam construction.

Safety closes the set with the practical principles — distance and shielding — selected against plausible-sounding non-principles.

The blind verification pass agreed with the stored key on all ten questions. Every value is given in the questions, matching the data-booklet exam format, and each explanation shows the exponential or ratio reasoning in full.

• Compare alpha, beta and gamma deflection, ionisation and penetration quantitatively
• Apply the inverse square law to gamma intensity
• Use half-life and the decay constant λ = ln2/T½ in exponential decay problems
• Scale nuclear radii with the A^(1/3) relation
• State activity units and practical radiation-safety principles

Topic scope follows section 3.8 (Nuclear physics) of the current A-level physics subject content: properties of nuclear radiation, the inverse square law, radioactive decay mathematics, nuclear radius estimation and safety.