What is the unit of measurement for radioactive activity?

The unit of measurement for radioactive activity is the Curie. This unit quantifies the amount of radioactive material in terms of its decay rate, specifically measuring the number of disintegrations that occur in a sample of radioactive material per second. One Curie is defined as the activity of a sample of radioactive material that disintegrates at the rate of 3.7 x 10^10 disintegrations per second. This measurement is crucial in fields such as nuclear medicine, radiology, and radiation safety, where understanding the level of a substance's radioactivity is necessary for safety measures and treatment planning.

The other units mentioned have different applications: the Rutherford is a less commonly used unit of activity, the Gray measures absorbed dose of radiation, and the Sievert assesses the biological effect of radiation on human tissues. Each of these serves specific purposes in radiation measurement but does not quantify the activity of radioactive materials like the Curie does.