Study Notes
Radioactive decay is the spontaneous disintegration of a nucleus, emitting alpha, beta, or gamma particles to form a more stable nucleus.
- Radioactive Decay — spontaneous disintegration of a nucleus emitting particles. Example: Alpha, beta, or gamma emissions.
- Randomness in Decay — decay events occur unpredictably. Example: Irregular counts in a Geiger-Muller tube.
- Decay Constant (λ) — probability of a nucleus decaying per unit time. Example: Higher λ means higher activity.
- Activity (A) — average number of decays per unit time, measured in Becquerels (Bq). Example: A = -λN or A = ΔN/Δt.
- Exponential Decay — rapid decrease in undecayed nuclei over time. Example: N = N₀e⁻λt.
- Half-life — time taken for the initial nuclei count to reduce by half. Example: After one half-life, activity reduces by half.
Exam Tips
Key Definitions to Remember
- Radioactive decay is the spontaneous disintegration of a nucleus.
- Decay constant (λ) is the probability of decay per unit time.
- Activity (A) is the average number of decays per unit time.
- Half-life is the time taken for the nuclei count to reduce by half.
Common Confusions
- Confusing randomness in decay with predictability.
- Misunderstanding the relationship between half-life and decay constant.
Typical Exam Questions
- What is radioactive decay? Radioactive decay is the spontaneous disintegration of a nucleus emitting particles.
- How is activity related to decay constant? Activity is calculated using A = -λN or A = ΔN/Δt.
- What happens to activity after one half-life? Activity reduces by half after one half-life.
What Examiners Usually Test
- Understanding of the random nature of radioactive decay.
- Ability to calculate activity and half-life using given formulas.