(a)[2]
What is meant by radioactive decay constant?
(b)[3]
A radioactive iodine-131 sample $\left(^{131}_{53}\text{I}\right)$ with a mass of $5.87 \times 10^{-10}\ \text{kg}$ has an activity of $2.92 \times 10^{9}\ \text{Bq}$. Determine the decay constant of iodine-131.
(c)[2]
Suggest two reasons why a detector placed close to the sample in (b) would register a count rate far below $2.92 \times 10^{9}$ counts per second.