X-rays work by passing electromagnetic radiation through the body to create an image on film or on a digital device, thus providing diagnostic imaging. They are a part of the electromagnetic spectrum that includes visible light, ultraviolet light and infrared red heat. X-rays are shorter in wavelength than visible light and heat.
While most X-rays pass through the soft tissues of the body, harder material, such as bone, surgical implants and metal plates block them. In an X-ray, the calcium in bones absorbs the greatest amount of the energy, so the bones appear as white on the negative image. Muscles and fat absorb some of the radiation, although less than bones, providing a gray image of the body. Since air does not absorb radiation, the lungs appear black. However, if the patient has fluid in the lungs, as with pneumonia or a tumor, the fluid absorbs some of the radiation, allowing the film to display anomalies.
While X-rays are important diagnostic tools, patients should limit their exposure to the radiation they emit. Many facilities help patients by providing lead shielding aprons, which provide a barrier against radiation and prevent potential exposure and damage by reducing the radiation exposure of areas that don't need imaging.