(a(1))[1]
State what spontaneous decay means.
(a(2))[1]
State what random decay means.
(b(i))[3]
Strontium-90 $\left(^{90}_{38}\text{Sr}\right)$ is an unstable nuclide. The activity of a sample of $1.0 \times 10^{-9}\,\text{kg}$ of strontium-90 is $5.2\,\text{MBq}$. Determine the decay constant $\lambda$ of strontium-90.
(b(ii))[1]
After a time of $1.0$ half-lives, the activity of the sample is greater than the expected $2.6\,\text{MBq}$. Suggest one possible reason for this.