P6 - Half Life

HALF-LIFE

Half Life = The TIME TAKEN for HALF of the radioactive nuclei now present to decay

As more unstable nuclei decay, the radiactivity of the source as a whole decreases (the OLDER a radiocative source is the LESS radiation it emits)

How quickly the activity decreases varies a lot. For some isotopes it takes just a few seconds before nearly all the unstable nuclei have decayed, others it takes millions of year.

The activity NEVER reaches zero which is why we have to use half life to see how quickly the activity decreases

Short half life= activity fell quickly, lots of the nulci decayed in a short time

Long half life= Activity fell slowly, most of the nuclei don't decay for a long time

1. Divide the highest point of activity by 2

2. Find this number on the axis and draw a horizontal line on the graph to find the half life