Question

calculate how long it would take for the following to decay to an activity of 1 becquerel (Bq).
1. A sample of cobalt-60(half-life - 5.27 years) whose original activity is 64 Bq.
2.A sample of iodine-131 (half-life - 8 days) whose original activity is 128 Bq.
3. A sample of polonium -210 (half-life - 138 days) whose original activity falls is 32 Bq.