What is the unit of measure for radioactivity?

The unit of measure for radioactivity is the Becquerel (Bq). This unit quantifies the activity of a radioactive material by measuring the number of nuclear decay events occurring per second. One Becquerel is defined as one decay per second, which provides a straightforward way to express the intensity of radioactivity in a sample.

Understanding that radioactivity is fundamentally about the rate of decay is essential for assessing the risk and managing exposure to radioactive materials in a safety context.

On the other hand, the Rutherford is a historical unit that has fallen out of common use. The Gray and the Sievert are units related to the effects of radiation on biological tissue; Gray measures absorbed dose, while Sievert measures the biological effect or dose equivalent, but neither directly represents radioactivity. Therefore, the Becquerel is the correct answer as it specifically addresses the measure of radioactivity itself.