In 15 hours there are 15 ÷ 3 half-lives = 5 half-lives.
After each half-life the count rate is halved.
After five half-lives the count rate is 17.
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Half-Life - Calculations.
1. If you are given
two count rates
and you know how long it takes to get
from one to the other,
then you can calculate
the half-life of the
material (next
page).
2. If you know the half-life of a
material,
you can calculate what the count rate will
be at some time in the future.
Question. The half-life of a material is 3
hours.
If the initial count rate is
544 Bq,
what will the count rate be after 15
hours?
Answer. Put the count rate in
boxes and use arrows to represent the half-life.
In 15 hours there are 15 ÷
3 half-lives = 5
half-lives.
After each half-life the count rate is
halved.
After five half-lives the count
rate is 17.
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