Beta (β) — fast electron emitted from nucleus (neutron → proton + electron). Stopped by 3mm aluminium. Moderately ionising.
Gamma (γ) — electromagnetic radiation from nucleus. Stopped by thick lead/concrete. Weakly ionising. High penetration.
Alpha is most dangerous inside the body (most ionising). Gamma is most dangerous outside (most penetrating).
Half-life
Half-life = time taken for half the radioactive nuclei in a sample to decay.
Also = time for activity to halve.
After n half-lives: activity = initial activity × (½)ⁿ.
Half-life is constant for a given isotope — not affected by temperature, pressure or chemical state.
Read from graph: find when activity = half its initial value → that time is one half-life.
Nuclear equations
Alpha decay: ²³⁸₉₂U → ²³⁴₉₀Th + ⁴₂He. Mass number drops by 4, atomic number drops by 2.
Beta decay: ¹⁴₆C → ¹⁴₇N + ⁰₋₁e. Mass number unchanged, atomic number increases by 1.
In all nuclear equations: mass numbers must balance, atomic numbers must balance.
Fission — large unstable nucleus splits into two smaller nuclei + neutrons + energy. Used in nuclear reactors.
Fusion — two light nuclei join to form a larger nucleus + energy. Powers the Sun. Very high temp/pressure needed.
Exam questions — 4 questions · 13 marks
⚡ Extended questions included. Show all working for calculation questions. The AI marks against the real AQA mark scheme.
1 markAlpha propertiesAQA 8463 P1 style
Why is alpha radiation the most ionising but least penetrating type of radiation?
A Alpha particles have a negative charge so they attract electrons from atoms but cannot travel far
B Alpha particles are large and slow — they interact strongly with atoms (high ionisation) but are absorbed after a short distance
C Alpha particles travel faster than gamma rays so they collide more often
D Alpha particles are electrically neutral so they only interact through gravity
3 marksHalf-life calculationAQA 8463 P1 style — real exam style
A radioactive source has an initial activity of 800 Bq. Its half-life is 3 hours. Calculate the activity after 12 hours. Show your working. (3 marks)
Hint: Calculate how many half-lives fit into 12 hours. Then halve the activity that many times.
+30 XP
3 marksNuclear equationAQA 8463 P1 style
Uranium-238 undergoes alpha decay. Write the nuclear equation for this decay, identifying the daughter nucleus. Show that both mass number and atomic number are conserved. (3 marks)
Hint: Alpha particle = ⁴₂He. Subtract 4 from mass number and 2 from atomic number. Check both balance.
+30 XP
1 markFission vs fusionAQA 8463 P1 style
Which statement correctly compares nuclear fission and fusion?
A Both fission and fusion are used in current nuclear power stations
B Fission splits heavy nuclei releasing energy; fusion joins light nuclei releasing even more energy per kg of fuel
C Fusion is safer than fission because it produces no radiation
D Fission requires very high temperatures; fusion does not
3 marksUses and dangers of radiationAQA 8463 P1 style
Explain why gamma radiation is used in medical imaging but alpha radiation is not. (3 marks)
Hint: Cover why gamma works (penetrating, detected outside body) AND why alpha cannot (stopped by skin, too ionising).