Radioactive decay
Example for carbon-14

Carbon-14 has a half-life of 5700(30) years and a decay rate of 14 disintegrations per minute (dpm) per gram of natural carbon.

If an artifact is found to have radioactivity of 4 dpm per gram of its present C, we can find the approximate age of the object using the above equation:

where:
startend:end_checker