Half Life Graphs IGCSE
The half life is the time it takes for the activity of a sample to half. Find the half lives
of the following samples.
Sample A
Activity of Sample (Bq)
Activity of Sample A Over 2 Minutes
120
100
80
60
40
20
0
0
20
40
60
80
100
120
140
Time (s)
Half Life = ________________
Sample B
Activity of Sample (Bq)
Activity of Sample B Over 10 Minutes
25000
20000
15000
10000
5000
0
0
100
200
300
400
Time (s)
Half Life = ________________
500
600
700
Half Life Graphs IGCSE
Sample C
Activity of Sample (Bq)
Activity of Sample C Over 1 000 000 Years
120000
100000
80000
60000
40000
20000
0
0
200000
400000
600000
800000
1000000
Time (years)
Half Life = ________________
Calculating Half Life:
Example: A sample of cobalt-60 has an activity of 2000 Bq. What will the activity be
after 10 years? Cobalt-60 has a half life of 5 years.
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Example: A sample of strontium-90 has an activity of 5000 Bq. After 120 years the
activity has fallen to 625 Bq. What is the half life of strontium-90?
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