©Department of Physics, University of Guelph.

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1. The physical half life of an isotope is
15 days. What is the corresponding decay constant in day^{-1} and
s^{-1}?

2. The values of l_{p}
and l_{b} for a particular radioactive
isotope in humans is 0.080 day^{-1} and 0.050^{-1} respectively.
What is the effective half life of the isotope in humans?

3. Two goats at Port Hopeless, Ontario accidentally
get into a field containing radioactive grass. The goat "Aristophanes"
eats twice as much grass as the goat "Demetrius". However Aristophanes'
metabolism is 1.5 times faster than that of Demetrius and the ingested
isotope has in this case a biological decay constant which is directly
proportional to metabolism. If the biological decay constant is 0.10 day^{-1}
in Demetrius, how long will it be until the two goats contain the same
concentration of isotope? Assume that the physical half life is very long
compared to the biological half lives.