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

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

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’.

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

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!

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

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

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?