- X-Ray
- Form of radiant energy with wavelength shorter than that of
visible light and with the ability to penetrate materials that
absorb or reflect ordinary light. X-rays are usually produced
by bombarding a metallic target with electrons in a high vacuum.
In nuclear reactions it is customary to refer to photons
originating in the nucleus as gamma rays and to those
originating in the extranuclear part of the atom as x-rays.