Half-life

• • Count rate is number of decays recorded each second by a detector
  • A Geiger-Muller tube is used to measure count rate
• • Half life is the time taken for the number of radioactive nuclei in an isotope to halve
• • A short half-life means activity falls quickly because nuclei are unstable and rapidly decay
  • Dangerous - high amount of radiation emitted at start
• • Long half life means activity falls slowly because nuclei doesn't decay for long time
  • Small amounts of radiation released for long time
  • Dangerous - nearby areas exposed to radiation for years