Comparing Half-Lives of Two Isotopes

Theory

The decay constant is $\lambda =\frac{\ln 2}{T_{1/2}}$ and the activity is $A=\lambda N$. An isotope with a short half-life starts with high activity but runs out quickly — this is why medical tracers (e.g. technetium-99m, 6 h) are chosen with short half-lives, while radiocarbon dating uses carbon-14 (5730 years).

What to observe

• After 6 s, the 2 s isotope has 1/8 left; the 6 s isotope has 1/2.

Try this

• Make both half-lives equal and compare the random fluctuations.

Also available in: Comparando meias-vidas de dois isótopos (Português) · Comparando semividas de dos isótopos (Español)