After five half-lives the count rate is 17 Bq.
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Using Half-life to Calculate the Count Rate.
Calculations using Half-life.
There are two types of calculation using half-life.
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.
The method for this is shown on the 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.
The method for this is shown below.
How Half-life
can be used to Calculate the Count Rate.
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.
We are told that the half-life of the material is 3
hours.
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
Bq.
Links
Radioactivity
Half-life
Revision Questions
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