Two mice each eat one-third of a piece of radioactive cheese, leaving one-third behind. Forty minutes later the two mice are caught and eaten by an owl. Six hours after this meal, the owl is caught and has a total body count of 200 counts per minute, which by coincidence is the same as the remaining piece of cheese at the same time. The effective half-life for the radioactive isotope in an owl is 4.00 h and in a mouse 1 h and 20 min. a) What is the biological half-life for this isotope in a mouse? (ans=100 min) b) What was the initial count-rate for the whole piece of cheese? The diagram might help you to organize your thoughts. (ans=1200 counts per minute)

Two mice each eat one-third of a piece of radioactive cheese, leaving one-third behind. Forty minutes later the two mice are caught and eaten by an owl. Six hours after this meal, the owl is caught and has a total body count of 200 counts per minute, which by coincidence is the same as the remaining piece of cheese at the same time. The effective half-life for the radioactive isotope in an owl is 4.00 h and in a mouse 1 h and 20 min.

a) What is the biological half-life for this isotope in a mouse? (ans=100 min)

b) What was the initial count-rate for the whole piece of cheese? The diagram might help you to organize your thoughts. (ans=1200 counts per minute)