P7: Radioactivity, Nuclear Decay and Half-Life
Official Cambridge & Imperial ESAT specification requirements for Radioactivity, Nuclear Decay and Half-Life on the Physics paper. Understand the syllabus boundaries, spot distractor traps engineered by examiners, and master the 2-step Sub-90 shortcuts that compress solve time well below the 88.8-second cutoff.
Official Syllabus Subtopics
Requirements specified in the UAT-UK framework
- 1Atomic number Z (protons) and mass number A (nucleons)
- 2Alpha decay (He-4 nucleus emitted: A-4, Z-2)
- 3Beta-minus decay (neutron turns to proton + electron: A unchanged, Z+1)
- 4Gamma radiation (electromagnetic emission: A and Z unchanged)
- 5Penetrating and ionising powers of alpha, beta, and gamma
- 6Background radiation subtraction and corrected count rates
- 7Half-life calculus: N(t) = N₀ × (½)ᵗ/ᵗ¹/²
- 8Nuclear fission (induced by neutron absorption) and nuclear fusion (requiring high temp/pressure)
Sub-90 Exam Speed Tips
How top candidates solve this spec under the 88.8s clock
Always subtract the background radiation count rate BEFORE halving the count rate to determine half-life.
In beta-minus decay, a neutron transforms into a proton, emitting an electron: nucleon number A stays identical.
Examiners engineer distractor options using common algebraic expansions and sign slips. Always test structural ratios or invariants before calculating arithmetic values.
Tested Topics in Specification P7
Master the individual question patterns and Sub-90 shortcuts for this specification.
Nuclear Decay Chains (α, β⁻, γ), Isotope Algebra & Background-Corrected Half-Life Calculus
Decay chain 2-step rule: (1) Mass number A only changes via alpha: N(alpha) = (A(start) - A(end))/4. (2) Proton number: N(beta) = Z(end) - (Z(start) - 2*N(alpha)). For count rates: Net = Raw - Background.
Ready to Master Specification P7 Under Exam Conditions?
Practice timed questions under the authentic Pearson VUE interface with live split stopwatch pacing, dry-wipe scratchpad, and distractor forensics.