In what unit is the activity of radioactive material measured?

The activity of radioactive material is measured in units of becquerels and curies. The becquerel (Bq) is the SI unit that defines one disintegration per second, indicating the quantity of radioactive decay occurring in a sample. The curie (Ci) is an older unit that corresponds to a large number of decays, specifically defined as 37 billion decays per second. While both units can be used to express the activity of radioactive materials, it's important to recognize that the becquerel is the standard unit endorsed by the International System of Units (SI).

Grays and sieverts, on the other hand, are units used to measure absorbed dose and equivalent dose, respectively, not the activity of radioactive materials. Grays quantify the amount of energy deposited in a material from ionizing radiation, while sieverts account for the biological effect of that radiation. Understanding the distinction between these units is crucial in radiation safety and health physics, as they pertain to different concepts in radiation measurement.