Scientists now know that X rays are one of several forms of electromagnetic radiation. Another form of such radiation is visible light. The various forms can be distinguished by their wavelength, the distance between successive crests of their waves. From the shortest wavelength to the longest, electromagnetic radiation consists of gamma rays, X rays, ultraviolet rays, visible light, infrared rays, and radio waves. 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.