X-radiation (composed of
X-rays) is a form of
electromagnetic radiation. X-rays have a
wavelength in the range of 10 to 0.01
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 120
eV to 120
keV. They are shorter in wavelength than
UV rays. In many languages, X-radiation is called
Röntgen radiation after
Wilhelm Conrad Röntgen, who is generally credited as their discoverer, and who had called them X-rays to signify an unknown type of radiation.
[3]1-2X-rays can penetrate solid objects, and their largest use is to take images of the inside of objects in diagnostic radiography and crystallography. As a result, the term X-ray is metonymically used to refer to a radiographic image produced using this method, in addition to the method itself. X-rays are a form of ionizing radiation, and exposure to them can be a health hazard.
X-rays from about 0.12 to 12 keV (10 to 0.10 nm wavelength), are classified as soft X-rays, and from about 12 to 120 keV (0.10 to 0.010 nm wavelength) as hard X-rays, due to their penetrating abilities.
The distinction between X-rays and gamma rays has changed in recent decades. Originally, the electromagnetic radiation emitted by X-ray tubes had a longer wavelength than the radiation emitted by radioactive nuclei (gamma rays).[4] So older literature distinguished between X- and gamma radiation on the basis of wavelength, with radiation shorter than some arbitrary wavelength, such as 10-11 m, defined as gamma rays.[5] However, as shorter wavelength continuous spectrum "X-ray" sources such as linear accelerators and longer wavelength "gamma ray" emitters were discovered, the wavelength bands largely overlapped. The two types of radiation are now usually distinguished by their origin X-rays are emitted by electrons outside the nucleus, while gamma rays are emitted by the nucleus.[4][6][7][8]
