Copper-66 is a radioactive isotope. When a copper-66 nucleus undergoes decay, the emissions include a $\beta^-$ particle and a $\gamma$-ray photon. The count rate from a sample of the isotope copper-66 is recorded with a detector and counter, as shown in Fig. 13.1.
(a)[3]
State three reasons why the activity of the copper-66 sample is not the same as the measured count rate.
(b)[2]
Over a period of $42.0\,\text{minutes}$, the count rate for the copper-66 sample falls from $3.62 \times 10^4\,\text{Bq}$ to $1.21 \times 10^2\,\text{Bq}$. Calculate the half-life of copper-66.
(c)[1]
The $\gamma$-ray photons released by radioactive nuclei have definite energies, and these depend on which nucleus emits them. Using the analogy with emission line spectra, suggest what can be inferred about energy levels in nuclei.
Worked solution & mark scheme
This 6-mark question has a full step-by-step worked solution and mark scheme. One marking point: “Any three suitable reasons, for example background radiation, multiple counts, isotropic emission, dead-time, instability of daughter nucleus, or absorption” …