The test relies on the fact that different parts of the body attenuate (stop) X-rays better than others. X-rays are ionising radiation, generated by an X-ray tube.
The rays are controlled by shielding down a narrow beam, directed towards the part of the body being examined. On the opposite side of the body, an x-ray film is positioned in the path of the x-rays, and is “exposed”.
The X-ray film is then processed and an image generated. Where the X-ray passes through the body easily, that part of the film will be black. Where x-rays are stopped, the film will be white and various shades of grey in between.
X-ray examinations are used to look at many structures in the body. They are especially good at looking at the chest and at the limbs, but plain X-ray is a very versatile imaging method.