©Department of Physics, University of Guelph.

 Click on the number or part you wish

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 lp and lb 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.

Return to Study Guide 7