Difference between revisions of "X-ray"
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| − | *Date: [ | + | *Date: [https://www.wikipedia.org/wiki/19th_Century 1896] |
==Definitions== | ==Definitions== | ||
| − | *1 : any of the [ | + | *1 : any of the [https://en.wikipedia.org/wiki/Electromagnetic_radiation electromagnetic radiations] that have an extremely short [[wavelength]] of less than 100 [[angstroms]] and have the properties of penetrating various thicknesses of all [[solids]], of producing secondary radiations by impinging on [[material]] [[bodies]], and of [[acting]] on photographic films and plates as [[light]] does |
*2 : a [[photograph]] obtained by use of X-rays | *2 : a [[photograph]] obtained by use of X-rays | ||
==Description== | ==Description== | ||
| − | ''X-radiation'' (composed of '''X-rays''') is a [[form]] of [ | + | ''X-radiation'' (composed of '''X-rays''') is a [[form]] of [https://en.wikipedia.org/wiki/Electromagnetic_radiation electromagnetic radiation]. X-rays have a [[wavelength]] in the range of 10 to 0.01 [https://en.wikipedia.org/wiki/Nanometer 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 [https://en.wikipedia.org/wiki/UV UV] rays and longer than [https://en.wikipedia.org/wiki/Gamma_ray gamma rays]. In many languages, X-radiation is called ''Röntgen radiation'', after [https://en.wikipedia.org/wiki/Wilhelm_R%C3%B6ntgen Wilhelm Conrad Röntgen], who is generally credited as their discoverer, and who had named them X-rays to signify an [[unknown]] [[type]] of [[radiation]]. |
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. | 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. | ||
| − | Hard X-rays can [[penetrate]] [[solid]] objects, and their largest use is to take images of the inside of objects in [[diagnostic]] [ | + | Hard X-rays can [[penetrate]] [[solid]] objects, and their largest use is to take images of the inside of objects in [[diagnostic]] [https://en.wikipedia.org/wiki/Radiography radiography] and [https://en.wikipedia.org/wiki/X-ray_crystallography crystallography]. As a result, the term X-ray is [https://en.wikipedia.org/wiki/Metonomy metonymically] used to refer to a radiographic image produced using this [[method]], in addition to the method itself. By [[contrast]], soft X-rays can hardly be said to penetrate [[matter]] at all; for instance, the attenuation length of 600 eV (~ 2 nm) x-rays in [[water]] is less than 1 micrometer. X-rays are a form of ionizing radiation, and exposure to them can be a [[health]] [[Risk|hazard]]. |
| − | The distinction between X-rays and [ | + | The distinction between X-rays and [https://en.wikipedia.org/wiki/Gamma_ray 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 [https://en.wikipedia.org/wiki/Radioactive radioactive] [https://en.wikipedia.org/wiki/Atomic_nucleus nuclei] (gamma rays). 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. However, as shorter wavelength [[continuous]] [[spectrum]] "X-ray" sources such as [https://en.wikipedia.org/wiki/Linear_accelerator 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]].[https://en.wikipedia.org/wiki/X_ray] |
[[Category: Physics]] | [[Category: Physics]] | ||
Latest revision as of 02:42, 13 December 2020
- Date: 1896
Definitions
- 1 : any of the electromagnetic radiations that have an extremely short wavelength of less than 100 angstroms and have the properties of penetrating various thicknesses of all solids, of producing secondary radiations by impinging on material bodies, and of acting on photographic films and plates as light does
- 2 : a photograph obtained by use of X-rays
Description
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 and longer than gamma rays. In many languages, X-radiation is called Röntgen radiation, after Wilhelm Conrad Röntgen, who is generally credited as their discoverer, and who had named them X-rays to signify an unknown type of radiation.
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.
Hard X-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. By contrast, soft X-rays can hardly be said to penetrate matter at all; for instance, the attenuation length of 600 eV (~ 2 nm) x-rays in water is less than 1 micrometer. X-rays are a form of ionizing radiation, and exposure to them can be a health hazard.
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). 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. 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.[1]
