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Mean life
Intermediate
Average lifetime of a nucleus.
τ = 1/λτ = 1/λ = 1.44 T½ is the average lifetime of a nucleus; the number falls to 1/e after τ.
T½ = 5730 yr gives τ = 8267 yr.
Mean life is longer than half-life.
In more detail
The mean life is the average lifetime of a radioactive nucleus, τ = 1/λ. It is longer than the half-life by a factor of about 1.44.
Real-world uses
- Mean life is used in particle physics to describe short-lived particles.
- It appears in decay calculations as the time constant.
- Nuclear engineers use the mean life to estimate how long a radioactive sample stays active on average.
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Frequently asked questions
How does mean life relate to half-life?
Mean life equals half-life divided by ln2, which is about 1.44 times larger.
Is mean life the same as the time most nuclei last?
It is an average, and some nuclei decay much sooner while others last longer.
Is mean life longer than half-life?
Yes. The mean life is about 1.44 times the half-life, because some nuclei survive much longer than the average.
Related topics in Atomic & Nuclear Physics
Gamma decay · Radioactive decay law · Half-life · Activity · Radioactive series · Carbon dating