Radioactive activity and the becquerel

The key idea

Activity is the expected number of nuclear decays per unit time. Its SI unit, the becquerel, equals one decay per second.

Why it matters

Activity depends both on how many unstable nuclei are present and on their decay constant: A = λN.

A picture to remember

Start with the central idea, then test it against a concrete element or example. A scientific model is useful when we know what it explains — and where its limits are.

The key idea

Activity is the expected number of nuclear decays per unit time. Its SI unit, the becquerel, equals one decay per second.

The key idea

Activity depends both on how many unstable nuclei are present and on their decay constant: A = λN.