ABSTRACT
Ranked by decreasing wavelength, X-rays or Roentgen rays occupy the high-frequency part of the electromagnetic spectrum in the series comprising radio waves, infrared light, visible light, ultraviolet light, soft and hard X-rays, and gamma radiation. X-rays were first artificially produced by stopping electrons in glass and other materials. Quantum electrodynamics explains the characteristics of X-rays up to the experimental limits. This theoretical framework comprises the quantum nature of electromagnetic waves, the quantum mechanical wave-like nature of electrons and other particles, and the relativistic effects of high kinetic energy. Electromagnetic waves, such as X-rays, arise when charge carriers such as electrons alter their velocity, either their direction or their absolute value, or both. Any nonzero second-time derivative of the position vector X gives rise to electromagnetic radiation. Atoms are stable, opposed to the classical picture, where the orbiting electrons would radiate.
