An aluminium block is placed near to a small source of X-ray radiation, as shown in figure I below.
I
X-rays from the source are detected at point A and at point B. State two reasons why the intensity of the X-ray beam at point B is not as great as the intensity at point A.
A cross-section through a model of a finger is shown in figure II below.
II
The thickness of the model is 
and that of the bone in the model is 
. Parallel beams of X-rays are incident on the model in the directions AB and CD, as shown in figure II above. Data for the linear attenuation (absorption) coefficient 
for the bone and the soft tissue in the model are given in figure III below.
III
Calculate the ratio
for
the beam AB,
the beam CD.
Use your answers in (b) to suggest why, for this model, an X-ray image with good contrast may be obtained.
