X-rays are a form of electromagnetic radiation, which is visible
light. The difference is that X-rays have a much shorter wavelength than visible light and
each X-ray particle, or photon, has much more energy than a photon partical of visible
light. Its short wavelength permits an X-ray to penetrate the body and produce an image on
film. Its high energy causes electrons to be dislodged from atoms and molecules when
X-rays strike them. This results in ion formation and causes tissue damage and,
potentially, cancer. Therefore X-rays are known as ionizing radiation.
When X-rays pass through the body, tissues of different degrees absorb them. Bones are absorbing the most and the air in the lungs and the intestines are absorbing the least. If a bone is in the path of the beam, few X-rays are striking the film, so it looks white. Convers, many X-rays strike the film when air is in the path of the beam, so that it looks black. Regular X-rays produce good pictures of bones and the lungs (chest X-ray), but in order to do some types of X-ray exams and to use artificial contrast media, you need a special preparation (go to "Preparation for exams").
What does most absorb the x-rays?