vacated space. The abrupt change in velocity when the attracted electron reaches its
final position results in the emission of an x-ray possessing an energy characteristic of
the target material.
Figure 2-2. X-ray spectrum.
h. The use of x-rays for radiography calls for hard x-rays--that is, x-rays with
energy high enough to penetrate the subject and expose the film. The x-ray beam also
contains a range of low energy or soft x-rays. These x-rays do not contribute anything
to radiography, but they can add to the patient's dose; therefore, we must remove these
soft x-rays from the beam. We do this by using a technique known as filtration. By
inserting a dense material into the beam, we can remove soft x-rays, thus leaving a
beam containing only hard x-rays. X-ray units come with the inherent filtration of their
components; however, we can provide additional filtration as may be required.
Materials such as aluminum or copper are used for additional filtration.