(a)[3]
State and explain how the hardness of the X-ray beam in an X-ray tube is controlled.
(b(i))[1]
A parallel beam of X-rays with intensity $I_0$ is incident on a medium whose linear absorption (attenuation) coefficient is $\mu$. State an equation for how the intensity $I$ changes with the thickness $x$ of the medium.
(b(ii))[2]
Fig. 11.1 shows data for the linear absorption (attenuation) coefficient $\mu$ for an X-ray beam in blood and in muscle. Suggest why using this X-ray beam to image blood vessels in muscle would give poor contrast on the image.