State how, in a modern X-ray tube, the intensity of the X-ray beam and its hardness are controlled.
A model of a limb consists of soft tissue and bone, as illustrated in the figure below.
The soft tissue has a thickness of 
. The bone within the soft tissue has a thickness of 
. Data for the linear attenuation (absorption) coefficient 
of X-rays in soft tissue and in bone are shown in the table below.
A parallel beam of X-rays of intensity 
is incident normally on the model. Calculate, in terms of :
the transmitted intensity 
through soft tissue alone
the transmitted intensity 
through soft tissue and bone.
By reference to your answers in (b), suggest, with a reason, whether good contrast on an X-ray image would be obtained.
.
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