X-ray

An X-ray is a high-energy photon with a wavelength shorter than ultraviolet light. X-rays are produced by energetic electrons slowing down or changing energy levels in atoms.

Bremsstrahlung: Electromagnetic radiation emitted when a charged particle, usually an electron, is accelerated or decelerated by another particle's electric field. Electrons striking a target slow down and emit the continuous X-ray spectrum.
Radiography: Imaging that forms a projection by measuring how radiation passes through an object. X-ray radiography maps differences in attenuation across a body or object.
Electromagnetic spectrum: The full range of electromagnetic radiation, ordered by frequency or wavelength. X-rays occupy the high-frequency region between ultraviolet radiation and gamma rays.
Wilhelm Conrad Röntgen: The German physicist who discovered X-rays in 1895 while studying cathode rays. Röntgen’s experiments first demonstrated the radiation now called X-rays.
Gamma ray: A high-energy photon commonly produced by nuclear transitions, particle interactions, or cosmic processes. Gamma rays overlap X-rays in energy but are conventionally distinguished by their nuclear or particle origins.
Characteristic X-ray: An X-ray photon emitted when an electron fills an inner-shell vacancy in an atom. The photon’s energy identifies the shell transition and therefore the target element.
Computed tomography: A medical imaging method that reconstructs cross-sectional images from multiple X-ray projections. It combines many X-ray measurements to recover three-dimensional internal structure.
Photon: The quantum of electromagnetic radiation, carrying energy and momentum. An X-ray is one photon in the high-energy part of the spectrum.
Cathode-ray tube: A vacuum tube in which electrons emitted by a cathode are accelerated toward an anode. Röntgen observed X-rays while operating a cathode-ray tube.
Ultraviolet: Electromagnetic radiation with wavelengths shorter than visible light and longer than X-rays. Ultraviolet photons generally have lower energies and longer wavelengths than X-rays.

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