GCSE Physics (AQA)

346 videos | 23 hours

Measuring Half-Life

Please subscribe to watch this video.

This, and all other videos, are included in our premium subscriptions.

Premium accounts get access to all videos.

Atomic structure Atoms and nuclear radiation

Measuring Half-Life

4:53 Half-Life
Spec 4.4.2.3
Previous Half-Life Next Half-Life Calculations
  • As nuclei in a radioactive source decay, the activity decreases.
  • Activity is the rate at which decays occur in a sample of unstable nuclei.
  • Over time, as nuclei decay, fewer are left to decay, reducing activity.
  • Half-life is the time it takes for the activity of a radioactive isotope to halve.
  • Half-life also describes the time it takes for the number of undecayed nuclei to halve.
  • Activity is proportional to the number of undecayed nuclei.
  • To measure half-life, calculate the count rate over time using a Geiger-M��ller tube.
  • The Geiger-M��ller tube detects radiation directed towards it, clicking for each decay.
  • Measure count rate at even time intervals and plot on a graph.
  • The graph shows a downward curve as count rate decreases over time.
  • Half-life is determined by the time it takes for the count rate to halve from any value.
  • Example: If count rate starts at 20, it halves to 10 in 1.5 minutes, then to 5 in 3 minutes, and to 2.5 in 4.5 minutes.
  • The half-life of the sample is 1.5 minutes.
  • Be confident in calculating half-lives from graphs for exams.

Please subscribe to access these revision notes.

This, and all other video notes, are included in our premium subscriptions.

Premium accounts get access to all videos and revision notes.