What is the half-life of Cesium-137?

Cesium-137 has a half-life of approximately 30 years. This means that after 30 years, half of the original quantity of Cesium-137 will have decayed into other isotopes, primarily Barium-137m, which is a decay product. This long half-life makes Cesium-137 significant for both medical applications and environmental concerns, as it remains radioactive for several decades. Its stability and longevity as a source of radiation make it useful in certain types of radiation therapy, as well as in industrial applications and as a tracer in various scientific research areas.

In contrast, the other options reflect much shorter half-lives. For example, a half-life of 6 hours would indicate rapid decay, which is characteristic of isotopes that are less stable, while 74 days still suggests a much shorter duration compared to Cesium-137. A half-life of 1600 years is characteristic of isotopes that are quite stable, but this is not representative of Cesium-137's behavior. Hence, the half-life of 30 years is a defining factor of Cesium-137's applications and risks.