Radioactivity Study Guide

Radioactive decay is a random process where unstable atomic nuclei spontaneously transform into more stable forms by emitting radiation. The 'activity' of a radioactive source quantifies the rate at which these decay events occur, measured in Becquerels (Bq), where 1 Bq corresponds to one decay per second. Over time, as more unstable nuclei decay, the total number of undecayed nuclei in a sample decreases. Consequently, the rate of decay also diminishes, causing the activity of the radioactive source to decrease. This reduction in activity is not linear but exponential, meaning it slows down over time. The half-life of a radioactive isotope is the time taken for the activity (or the number of undecayed nuclei) to halve. Each half-life period sees the activity reduced by half, demonstrating the exponential nature of decay. Eventually, if enough time passes, the activity will approach zero as almost all unstable nuclei will have decayed into stable daughter products.

Radioactivity is the process by which an unstable atomic nucleus loses energy by emitting radiation. This process is random and spontaneous. The 'activity' of a radioactive substance quantifies the rate at which its unstable nuclei decay or disintegrate. This rate is fundamental to understanding how quickly a radioactive source is losing its radioactive properties. The unit for measuring this activity is the Becquerel, symbol Bq. One Becquerel is defined as one disintegration or decay per second. This unit helps scientists and medical professionals to safely handle and apply radioactive materials by providing a standardised measure of their emitted radiation intensity.