Thus, X rays have a shorter wavelength, but more energy, than do waves of visible light. X rays can produce biological, chemical, and physical changes in the substances they enter. For this reason, X rays can be dangerous. In human beings, an overdose of X rays may cause cancer, skin burns, anemia, or other serious conditions. But physicians also use X rays to treat cancer.
X rays kill cancer cells more readily than they kill normal cells.
In X-ray machines used in medicine and science, a special tube that resembles a television picture tube produces X rays. Scientists also use intense, narrow beams of X rays generated by devices called synchrotrons. Radiographs help physicians detect injuries and diseases, such as broken bones or tumors, inside a patient's body. Dentists take X-ray pictures to reveal cavities in teeth. Because X rays can harm living tissue, health workers who use them in diagnostic work give their patients only as much radiation as necessary.