What is the SI unit of radioactivity?

The SI unit of radioactivity is the Becquerel. This unit quantifies the activity of a radioactive substance, indicating the rate at which decay events occur within that substance. Specifically, one Becquerel corresponds to one decay event per second.

Using the correct unit is essential in fields like medical dosimetry and radiation safety, as it allows professionals to communicate and measure radioactivity consistently. The adoption of the Becquerel as the standard unit within the International System of Units (SI) emphasizes the importance of a coherent framework for scientific measurement.

In contrast, the other options refer to different concepts within radiation measurements. The Curie is an older unit of radioactivity that was historically used but is not part of the SI system. The Gray is a unit of absorbed radiation dose, while the Sievert is a unit that measures the biological effect of ionizing radiation. These measurements are related to radiation exposure and its impact on human health, but they are not measures of radioactivity itself.