(a)
A parallel X-ray beam of intensity $I_0$ falls on either bone or muscle. The beam that emerges has intensity $I$. Calculate the ratio $\frac{I}{I_0}$ for a thickness of (i) $1.5\,\text{cm}$ of bone, (ii) $4.6\,\text{cm}$ of muscle.
(a(i))[2]
Calculate $\frac{I}{I_0}$ for bone with thickness $1.5\,\text{cm}$.
(a(ii))[1]
Calculate $\frac{I}{I_0}$ for muscle with thickness $4.6\,\text{cm}$.
(b)[3]
Suggest why, on an X-ray plate, the contrast between bone and muscle is much greater than the contrast between fat and muscle.