What do becquerels and curies measure in the context of radiation?

Becquerels (Bq) and curies (Ci) are units used to measure the activity of a radioactive substance. Activity refers to the rate at which a radioactive material undergoes decay or disintegration, which results in the emission of radiation. Specifically, one becquerel is defined as one disintegration per second, while one curie is equivalent to 37 billion disintegrations per second. Therefore, when assessing the level of radioactivity in a sample, becquerels and curies provide the necessary metrics for understanding how many atoms are decaying per unit time, thus quantifying the overall activity of the radioactive material.

In contrast, intensity of radiation, exposure levels, and energy levels relate to different aspects of radiation measurement. Intensity concerns how strong the radiation is, while exposure levels involve the amount of radiation an object or person is subjected to. Energy levels refer to the energy carried by the particles emitted, which does not directly relate to the rate of the radioactive decay measured by activity. This distinction highlights why the correct response focuses on activity as it specifically addresses the measurement that becquerels and curies represent.