Half-Life

This lesson covers half-life — one of the most important concepts in radioactivity — as required by the Edexcel GCSE Physics specification (1PH0), Topic 6: Radioactivity. You need to understand the random nature of radioactive decay, the definition of half-life, how to calculate the amount of radioactive material remaining after a given number of half-lives, and how to read half-life values from decay curves.

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The Random Nature of Radioactive Decay

Radioactive decay is a random process. This means:

• You cannot predict when a particular individual nucleus will decay.
• You cannot make a nucleus decay by heating it, cooling it, applying pressure, or any other physical or chemical change.
• However, for a large number of nuclei, you can predict how many will decay in a given time.

This is similar to rolling dice — you cannot predict which specific dice will land on a six, but you can predict that roughly one-sixth of a large number of dice will.