Complete the decay equation. $^{211}_{84}\text{Po} \rightarrow \,\ldots\ldots\text{Pb} + \,\ldots\ldots\alpha$
Fig. 9.1 shows how the number of unstable nuclei $N$ in a polonium-211 sample varies with time $t$. At time $t = 0$, the sample consists only of polonium-211.
Use Fig. 9.1 to find the decay constant $\lambda$ for polonium-211. Give the unit with your answer.
Use your answer in (b)(i) to calculate the activity of the polonium-211 sample at time $t = 0$.
On Fig. 9.1, sketch a line that shows how the number of lead nuclei in the sample varies with $t$.
An alpha particle is released in each decay with an energy of $6900\,\text{keV}$.
Calculate, in J, the total energy transferred to alpha particles emitted between time $t = 0.30\,\text{s}$ and time $t = 0.90\,\text{s}$.
Suggest why the total energy released by the decay process during the interval from time $t = 0.30\,\text{s}$ to time $t = 0.90\,\text{s}$ is greater than your answer in (c)(i).