Half-life

The half-life of an isotope is an important concept in understanding radioactive decay and its applications. This section will help you understand what half-life is, how to calculate it, and how it is used in real-life scenarios.

What is half-life?

The half-life of a radioactive isotope is defined as:

• The time taken for half the nuclei of that isotope in any sample to decay.

• It is a measure of how quickly or slowly an isotope undergoes radioactive decay.

For example, if an isotope has a half-life of 10 years, this means that after 10 years, half of the radioactive nuclei will have decayed. After another 10 years (making it 20 years total), only a quarter of the original radioactive nuclei will remain.

Using Half-Life in Calculations:

• The concept of half-life can be used in simple calculations to determine how much of a radioactive sample remains after a certain amount of time.

• This information might be given in tables or shown on decay curves. For calculations, it is assumed that background radiation is not included.

Calculating half-life from data or decay curves

You may be asked to calculate the half-life of an isotope using data or a decay curve.

• Decay Curves:

  • A decay curve is a graph that shows the decline of radioactive material over time.

  • By looking at the curve, you can determine how long it takes for the activity of the isotope to reduce by half, which is the half-life.

• Tables:

  • Data tables might provide counts of radioactive emissions at regular intervals. You can identify the half-life by determining how long it takes for the activity or the number of remaining radioactive nuclei to halve.

When calculating half-life, it's important to understand that background radiation is not included in the values given, and you only need to focus on the change in the isotope’s activity.

Half-life decay curve