Half-life Flashcards
What is half-life?
The time taken for half of the radioactive atoms now present to decay (or the time taken for the activity to fall by half).
How does radioactive decay work?
Each time a decay happens and an alpha or beta particle or gamma ray is given out, it means one more radioactive nucleus has disappeared.
What happens as the unstable nuclei disappear?
The activity decreases
What is activity?
The number of decays in a given time period
How does the time it takes for the activity to drop off change?
It varies - some take a few hours, others take millions of years.
What does a short half-life mean?
The activity falls quickly because the nuclei decay straightway and rapidly.
What does a long half-life mean?
The activity falls slowly because they take a long time before they start to decay.
How to calculate half life
1) Deduce how many times the original isotope has to be divided by 2 before it reaches its final state.
2) Find out how long this takes.
3) Calculate how long it takes for 1 full decay.
What is important to remember?
Subtract the background count from your values
