(a)[5]
Distinguish between an X-ray image of a body structure and a CT scan. X-ray image: ________. CT scan: ________.
(b)
Figure 11.1 gives data for the linear absorption (attenuation) coefficient $\mu$ of X-ray radiation with energy $80\,\text{keV}$. As shown in Fig. 11.2, a parallel X-ray beam falls on a copper filter. The intensity of the incoming beam is $I_0$.
(b(i))[2]
Calculate the thickness of copper needed to lower the intensity of the emergent beam to $0.25 I_0$.
(b(ii))[2]
An aluminium filter with thickness $2.4\,\text{mm}$ is now added to the X-ray beam, together with the copper filter in (i). Calculate the fraction of the incident intensity that comes out after passing through both filters.
(b(iii))[3]
Express your answer in (ii) as a gain in decibels (dB).