Question

If the activity of a source is 70 Bq after 2 years, and 35 Bq after 15 years. How long will be until the activity is 8.75 Bq?​

Answer 1

So if the half-life is two days, four half-lives is 8 days. Suppose a sample has a count rate of 3,200 Becquerel (Bq) at the start, then its count rate after 8 days would be 1/16th of 3,200 Bq = 200 Bq.