Grade 11 physics
Radioactivity and the Law of Radioactive Decay
Radioactive decay is random for one nucleus but statistically predictable for a large population through the decay constant and half-life.
1. Core ideas and learning goals
- Each unstable nucleus decays randomly with a constant probability per unit time under ordinary conditions.
- For a large sample, the expected number remaining follows N = N0 exp(-lambda t).
- Half-life is the time for the expected number of undecayed nuclei and activity to fall by one half.
- Activity A = lambda N is measured in becquerels, where one becquerel is one decay per second.
- Alpha, beta and gamma radiation differ in charge, penetration and interaction, so shielding and monitoring must match the source.
2. Physical model
Radioactive decay is random for one nucleus but statistically predictable for a large population through the decay constant and half-life.
Radioactive decay is random for one nucleus but statistically predictable for a large population through the decay constant and half-life. The model links observable changes with measurable physical quantities and conservation laws.
Before applying a relation, specify the reference frame, system boundary, initial state and approximations. The conclusion is valid only while those conditions are satisfied.