Problems
(1) Iodine-131 has a half-life of 8 days. If you started with a 12.0-mg sample of I-131, how much would remain after 24 days?
(2) Plutonium-239 is a byproduct of the fission reaction used to produce energy in nuclear power reactors. It has a half-life of 24,400 years. A student determines that it will take 97,600 years for the radioactivity of a Pu-239 sample to drop to one-eighth of its original level. Show calculations to support or refute her conclusion.
(3) Strontium-90 is present in the fallout produced by nuclear weapons testing in the atmosphere. Sr-90 is potentially dangerous to humans and animals because it substitutes chemically for calcium in bones and has a half-life of almost 29 years. What percent of the original amount of Sr-90 remains in a 61 year-old woman who unknowingly drank Sr-90 in contaminated milk when she was 3 years old?