Summary
Radioactive decay is the process by which unstable atomic nuclei lose energy by emitting radiation, resulting in a more stable nucleus. This process is random and spontaneous, unaffected by external conditions.
- Background Radiation — radiation from natural and artificial sources present in the environment. Example: Cosmic rays and radon gas.
- Alpha Particles — consist of 2 protons and 2 neutrons, emitted by large nuclei. Example: Helium nucleus emitted from uranium decay.
- Beta Particles — high-energy electrons emitted from the nucleus when a neutron turns into a proton. Example: Electron emitted during carbon-14 decay.
- Gamma Rays — high-energy electromagnetic waves emitted by nuclei to lose excess energy. Example: Gamma radiation from cobalt-60.
- Decay Constant (λ) — probability of an individual nucleus decaying per unit time. Example: Higher λ means faster decay.
- Half-life — time taken for half the nuclei in a sample to decay. Example: Carbon-14 has a half-life of about 5730 years.
Exam Tips
Key Definitions to Remember
- Background Radiation
- Alpha Particles
- Beta Particles
- Gamma Rays
- Decay Constant
- Half-life
Common Confusions
- Confusing alpha particles with helium atoms.
- Misunderstanding that gamma rays have mass.
Typical Exam Questions
- What is the half-life of a radioactive substance? The time taken for half the nuclei in a sample to decay.
- How does a Geiger-Muller counter work? It detects ionizing radiation by counting the number of decays.
- What is the difference between alpha and beta decay? Alpha decay emits a helium nucleus, while beta decay emits an electron.
What Examiners Usually Test
- Understanding of decay equations and their implications.
- Ability to calculate half-life from given data.
- Knowledge of the properties and differences between alpha, beta, and gamma radiation.