Theory
Reading the half-life from a decay graph
The half-life is the time in which the amount halves.
Read from the graph when the initial value is reached and when the half value is reached.
The difference between those two times is the half-life.
- Read two timesTake the time at the initial value and at the half value from the graph.
- Calculate the time differenceWork out the intermediate step using the values from the problem.
In a decay graph, the amount has halved between t = 0 hours and t = 8 hours. Calculate the half-life.
- Read two timesStart time = 0 hours. Time at half value = 8 hours.
- Calculate the time difference8 - 0 = 8 hours.