<P> X-rays make up X-radiation, 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 Hz to 3 × 10 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 the German scientist Wilhelm Röntgen, who usually is credited as its discoverer, and who 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). </P> <P> German physicist Wilhelm Röntgen is usually credited as the discoverer of X-rays in 1895, because he was the first to systematically study them, though he is not the first to have observed their effects . He is also the one who gave them the name "X-rays" (signifying an unknown quantity) though many others referred to these as "Röntgen rays" (and the associated X-ray radiograms as, "Röntgenograms") for several decades after their discovery and even to this day in some languages, including Röntgen's native German . </P>

Who invented the photographic effect that is known as x-rays