What does the activity of a radiation source refer to?

The activity of a radiation source is specifically defined as the rate at which it emits radiation over a certain period of time. This is typically measured in units like becquerels (Bq) or curies (Ci), where one becquerel corresponds to one decay event per second. Therefore, when referring to the amount of radiation emitted over time, it captures the essence of what is meant by the source's activity.

Understanding this concept is essential because activity provides insight into the strength and potential hazard associated with a radioactive source. It indicates not only how much radiation is present but also helps in establishing safety protocols and understanding the biological impacts on living organisms.

The other options touch on aspects of radioactivity but do not accurately describe what "activity" means in the physics of radiation. While radioactive capacity might suggest the potential for producing radiation, it does not define how much radiation is emitted. The speed of particle emission could relate to the dynamics of decay but does not quantify the overall radiation output across time. Potential for decay pertains to the likelihood of a particular isotope undergoing radioactive decay but lacks a direct connection to the measurement of radiation release over time.