1. 23/02/2019
Half Life
Learning Objective: express radioactivity using an exponential function

2. Group Stages Final Semi Quarter
This is a good analogy of radioactive decay – the decrease in teams (pick any sporting event!) is proportional rather than by a fixed amount each time.
Group Stages

3. We call this type of decay ‘exponential’.
In any given time period there is a fixed chance of atoms giving off radiation and decaying to become stable.
We call this type of decay ‘exponential’.

4. Half Life
As a radioactive sample emits radiation it becomes more stable so in future gives out less radiation
The time taken for half a sample to decay is called the half life
Half life is a constant for a given material and doesn’t depend on outside conditions

5. Nuclear Engineers
As part of their work nuclear engineers work with scientists to decide how and when to dispose of radioactive waste
As part of this work they must know how quickly this waste decays to safe levels of radioactivity
To do this they make use of their maths – particularly exponential decay!

6. The cube experiment 1 in 6 sides of the cubes are black
When rolled black facing cubes are removed
The remaining cubes are then rolled again with black facing cubes removed
On average 1/6th of cubes should be removed each time
This means it is exponential

7. Conclusions from cube experiment
Assuming each throw was 10 seconds apart what was the half life of the cubes experiment
The number of cubes at any time can be represented by
Calculate a value for λ based upon your results

8. Evaluation of cubes experiment
How appropriate was the cubes experiment as a way of modelling radioactive decay? Did the model give the results you were expecting?
How could you improve your experiment to make it more reliable/valid?
How could you expand upon your experiment for further study?