What is meant by gamma radiation ($\gamma$-radiation)?
A gamma radiation source is set a fixed distance from a detector and counter, as shown in Fig. 13.1. A lead sheet of thickness $x$ is placed between the source and the detector. The mean count rate $C$, after background correction, is measured. This is repeated for a range of $x$ values. Gamma radiation absorption in lead can be described by $C = C_0 e^{-\mu x}$, where $C_0$ is the count rate when $x = 0$ and $\mu$ is the linear attenuation (absorption) coefficient. Use Fig. 13.2 to find the linear attenuation coefficient $\mu$ for this gamma radiation in lead.
The value of $\mu$ found in (b) applies to gamma radiation in lead. Suggest and explain whether the value of $\mu$ for aluminium would be the same, larger or smaller.