half life

• Radioactive decay


  The process in which unstable atomic nuclei break apart or change, releasing radiation as they do so
• Radioactive decay is a random process
• Not all nuclei in a block of radioactive material are likely to decay at the same time
• It is impossible to tell when a particular nucleus will decay
• Scientists cannot tell when a particular nucleus will decay, but they can use statistical methods to tell when half the unstable nuclei in a sample will have decayed
• Half-life


  The time it takes for the number of nuclei of a radioactive isotope in a sample to halve, or for the activity of the sample to halve, or for the count rate to halve
• Half-life is the time it takes for half of the unstable nuclei in a sample to decay or for the activity of the sample to halve or for the count rate to halve
• Count-rate is the number of decays recorded each second by a detector, such as the Geiger-Muller tube
• Radioactive isotopes


  • Carbon-14
  • Cobalt-60
• The half-life of radioactive carbon-14 is 5,730 years
• Calculating the isotope remaining - Higher


  Express the amount of a sample remaining after n half-lives as a fraction, decimal or ratio