K-40

Potassium-40 (K-40) is a naturally occurring radioactive isotope of potassium with a half-life of approximately 1.25 billion years. It undergoes decay via beta emission and electron capture, producing argon-40 and calcium-40. As one of the primary sources of natural radioactivity, K-40 contributes to background radiation and is present in trace amounts in all potassium-containing materials.

K-40 has applications in geological and archaeological dating. Its decay to argon-40 is the basis of the potassium-argon dating method, widely used to determine the age of rocks, minerals, and volcanic materials, providing critical insights into Earth's history and evolution. K-40 also plays a role in understanding natural radiation doses, as it is a significant contributor to human exposure from natural sources.

Potassium-40 is found in nature as a small fraction of natural potassium, present in soils, rocks, and oceans. It is also found in food sources rich in potassium, such as bananas, potatoes, and certain nuts, making it an integral part of the human diet and environment. Despite its radioactivity, the levels of K-40 in natural settings are low and pose no significant health risk.

Potassium-40 is found almost everywhere, its peak is observed on all background spectra.