X-rays

X-rays can penetrate solid objects, and their largest use is to take images of the inside of objects in diagnostic radiography and crystallography. As a result, the term X-ray is metonymically used to refer to a radiographic image produced using this method, in addition to the method itself. X-rays are a form of ionizing radiation, and exposure to them can be a health hazard. In medical diagnostic applications, the low energy (soft) X-rays are unwanted, since they are totally absorbed by the body, increasing the dose. So a thin metal often aluminum, but can be one of many X-ray filters sheet is placed over the window of the X-ray tube, filtering out the low energy end of the spectrum. This is called hardening the beam. To take an X-ray of the bones, short X-ray pulses are shot through a body with radiographic film behind. The bones absorb the most photons by the photoelectric process, because they are more electron-dense. The X-rays leave a latent image in the photographic film; when it is subsequently developed, the parts of the image corresponding to higher X-ray exposure are dark, leaving a white shadow of bones on the film. A specialized source of X-rays which is becoming widely used in research is synchrotron radiation, which is generated by particle accelerators. Its unique features are brightness many orders of magnitude greater than X-ray tubes, wide spectrum, high collimation, and linear polarization.