t1/2
0.693
0.693
t1/2
0.693
7.13 seconds
0.0972 second1
A
Ao e
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RADIOACTIVITY
DOE-HDBK-1019/1-93
Atomic and Nuclear Physics
NP-01
Page 36
Rev. 0
Example:
Plot the radioactive decay curve for nitrogen-16 over a period of 100 seconds. The
initial activity is 142 curies and the half-life of nitrogen-16 is 7.13 seconds. Plot the
curve on both linear rectangular coordinates and on a semi-log scale.
Solution:
First, use Equation (1-6) to calculate the decay constant corresponding to a half-life of
7.13 seconds.
Use the decay constant determined above to calculate the activity at various times using
Equation (1-5).
Time
Activity
0 seconds
142 Ci
20 seconds
20.3 Ci
40 seconds
2.91 Ci
60 seconds
0.416 Ci
80 seconds
0.0596 Ci
100 seconds
0.00853 Ci
