Question

Define activity of a radioactive substance. Write its si unit

Answer 1

The activity of a radioactive substance is the rate of decay or the number of disintegrations per second of the substance.

The SI unit for activity is Becquerel, named after the discoverer of  radioactivity, Henry Becquerel.

Answer 2

Explanation:

Radioactive decay is the process by which an unstable atomic nucleus loses energy by radiation. A material containing unstable nuclei is considered radioactive. Three of the most common types of decay are alpha decay, beta decay, and gamma decay, all of which involve emitting one or more particles or photons.