X ray

A high-energy photon, usually produced by cathode rays or emitted by electrons falling to lower energy states in atoms. The range of frequencies in the electronic spectrum lying between the ultraviolet (3x1016Hz) and the gamma rays (1021Hz), wavelengths from a few picometers up to 20 nanometers.

Some properties of X-rays:

Discovered by Willhelm Conrad Röntgen (1845-1923) in November 1895.

Usually produced by fast electrons going through matter or by the de-excitation of excited atoms.

They are used to take medical photographs of internal organs and bones.

X-rays in high doses can damage living cells.

Hard X-rays

Higher-energy part of the X-ray spectrum ranging from approximately 5 keV to 100 keV.

Soft X-rays

Band of low energy X-rays, between 0.1 keV and approximately 5 keV.


A metallic object placed in the beam of electrons to produce x-rays.

See also: Angstrom Star, Characteristic X-ray, Coolidge, William D, Gamma Rays, Radionuclide, Siegbahn Unit, Ultraviolet Light, X-Ray Spectrum.

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