If a radioactive isotope has a decay constant of 0.308 s−1, what is the mean lifetime of an atom of that isotope? Give your answer to 3 significant figures.
Carbon-11 has a half-life of 20.3 minutes. The activity of a sample of pure carbon-11 is found to be 7,200 Bq. What will the activity of the sample be 4 hours later? Give your answer to 3 significant figures.
What is the average amount of time it takes for an atom of a radioactive isotope to decay, as a ratio of the half-life of the isotope?