Exponential Decay
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| The more air there is in the tyre the more air escapes every second | The hotter the cup of tea the quicker its temperature falls | The more rabbits you have the more rabbits will be born every week | The more people own the latest gadget the more are sold every week | The more unpopped corn there is the more corn pops every second |
In the examples above how quickly a quantity changes depends on how much of it there is.
Which are exponential decays and which are exponential growths?
If an isotope has a large decay constant then the activity is large so it will decay quickly. There must therefore be a relationship between the half life and the decay constant.
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If you know the decay constant you can
work out the half life and vice versa
If you know the number of parent atoms and the decay constant you can work out the activity |
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To use the equation you'll need to be familiar with
the ex button on your calculator.
A question might give the half life in minutes or years. If you want to calculate the activity in counts per second don't forget to convert the half life to seconds first. |
