568
Nuclear Structure
Q44.10
4
He
,
16
O
,
40
Ca
,
and
208
Pb.
Q44.11
If one half the number of radioactive nuclei decay in one year, then one half the remaining number
will decay in the second year. Three quarters of the original nuclei will be gone, and one quarter will
remain.
Q44.12
The statement is false. Both patterns show monotonic decrease over time, but with very different
shapes. For radioactive decay, maximum activity occurs at time zero. Cohorts of people now living
will be dying most rapidly perhaps forty years from now. Everyone now living will be dead within
less than two centuries, while the mathematical model of radioactive decay tails off exponentially
forever. A radioactive nucleus never gets old. It has constant probability of decay however long it
has existed.
Q44.13
Since the samples are of the same radioactive isotope, their halflives are the same. When prepared,
sample A has twice the activity (number of radioactive decays per second) of sample B. After 5 half
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 Fall '11
 Staff
 Physics, Electron, Radioactive Decay, forty years, radioactive nuclei decay, 208 Pb

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