The α, β and γ comparison table, N = N₀e^(−λt) with activity in becquerels and curies, half-life and mean life τ = 1.44 T, carbon dating worked through, and the medical radioisotopes.
Unit 6 carries 12 of the 50 physics marks, the largest share of any physics unit, and with seven chapters sharing them this one averages a little under two (MEC publishes weights by unit, not by chapter). Radioactivity is the friendliest of the seven to prepare: almost all of it is one comparison table, one exponential law and a handful of numbers.
The MEC scope lines are: Laws and units of radioactivity; properties of alpha, beta and gamma rays; Half-life, mean life and their relation; carbon dating; Medical uses of nuclear radiation and health hazards. The three headings below are those three points, in MEC's order.
Three ways it is asked: recall (which radiation is which, penetrating power in order, the units, half-lives of the named medical isotopes, who discovered what); understanding (why a decay is random but a half-life is precise, why temperature and chemical state make no difference, why a short-lived γ emitter is chosen for imaging and a long-lived β emitter is not, how to read the N-against-t curve); application (fraction left after a number of half-lives, λ from T, activity of a stated mass, a carbon date, the mass number and atomic number after a chain of emissions).
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