X-radiation (composed of
X-rays) is a form of
electromagnetic radiation. Most X-rays have a
wavelength ranging from 0.01 to 10
nanometers, corresponding to
frequencies in the range 30
petahertz to 30
exahertz (3×10
16 Hz to 3×10
19 Hz) and energies in the range 100
eV to 100
keV. X-ray wavelengths are shorter than those of
UV rays and typically longer than those of
gamma rays. In many languages, X-radiation is referred to with terms meaning
Röntgen radiation, after
Wilhelm Röntgen, who is usually credited as its discoverer, and who had named it
X-radiation to signify an unknown type of radiation. Spelling of
X-ray(s) in the English language includes the variants
x-ray(s),
xray(s), and
X ray(s).