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| [[File:lighterstill.jpg]][[File:Dbclusters_x_ir.jpg|right|frame]] | | [[File:lighterstill.jpg]][[File:Dbclusters_x_ir.jpg|right|frame]] |
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− | *Date: [http://www.wikipedia.org/wiki/19th_Century 1896] | + | *Date: [https://www.wikipedia.org/wiki/19th_Century 1896] |
| ==Definitions== | | ==Definitions== |
− | *1 : any of the [http://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 | + | *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 [http://en.wikipedia.org/wiki/Electromagnetic_radiation electromagnetic radiation]. X-rays have a [[wavelength]] in the range of 10 to 0.01 [http://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 [http://en.wikipedia.org/wiki/UV UV] rays and longer than [http://en.wikipedia.org/wiki/Gamma_ray gamma rays]. In many languages, X-radiation is called ''Röntgen radiation'', after [http://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-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]]. |
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| 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. |
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− | Hard X-rays can [[penetrate]] [[solid]] objects, and their largest use is to take images of the inside of objects in [[diagnostic]] [http://en.wikipedia.org/wiki/Radiography radiography] and [http://en.wikipedia.org/wiki/X-ray_crystallography crystallography]. As a result, the term X-ray is [http://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]]. | + | 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]]. |
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− | The distinction between X-rays and [http://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 [http://en.wikipedia.org/wiki/Radioactive radioactive] [http://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 [http://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]].[http://en.wikipedia.org/wiki/X_ray] | + | 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] |
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| [[Category: Physics]] | | [[Category: Physics]] |