قانون براگ: تفاوت میان نسخه‌ها

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{{در دست ویرایش ۲|ماه=ژوئن|روز=۷|سال=۲۰۰۸|چند = 2}}
در فیزیک '''قانون براگ''' نتایج آزمایشاتی است که از تابش [[پرتو ایکس]] یا [[نوترون]] به سطح [[بلور]]ین تابیده می شد derivedکه byبرای physicistاولین [[Williamبار Lawrenceتوسط Bragg|Sirفیزیکدان William[[ویلیام Lawrenceلاورنس Braggبراگ]] بررسی شد<ref> There are some sources, like the ''Academic American Encyclopedia'', that attribute the discovery of the law to both W.L Bragg and his father W.H. Bragg, but the official [http://nobelprize.org/nobel_prizes/physics/laureates/1915/present.html Nobel Prize site] and the biographies written about him (''Light Is a Messenger: The Life and Science of William Lawrence Bragg'', Graeme K. Hunter, 2004 and “Great Solid State Physicists of the 20th Century", Julio Antonio Gonzalo, Carmen Aragó López) make a clear statement that William Lawrence Bragg alone derived the law. </ref> inکه [[1912]]آزمایشاتش andدر first presented onسال [[1912-11-11۱۹۱۱ (میلادی)|۱۹۱۱]] toو theدر [[Cambridgeدانشگاه Philosophical Societyکمبریج]]. Althoughانجام simple,شد. Bragg'sبه lawطور confirmedساده theهنگام existenceتابانیدن ofپرتوهایی realمانند [[Subatomicپرتو particle|particle]]sایکس atیا theنوترون atomicبه scale,سطوح asبلورین wellبازتابش‌هایی asانجام providingمی aگیرد powerfulکه newبه toolاین forبازتاب studyingها [[crystal]]sپراش inیا theفرانژ formگویند, ofکه [[X-rayبه diffraction|X-ray]]همین andدلیل [[neutronویلیام diffractionبراگ]]. William Lawrence Bragg and his father, [[Williamجایزه Henryنوبل Bragg|Sirدر William Henry Braggفیزیک]], wereرا awardedدر theسال [[Nobel۱۹۱۵ Prize(میلادی)|۱۹۱۵]] inبه [[physics]]دست inآورد [[1915]]سطوح forبلورینی theirکه workاو inبررسی determiningکرده crystalبود structures beginning withعبارتنداز [[Sodiumکلرید chlorideسدیم|NaCl]], [[Zincسولفید sulfideروی|ZnS]], andو [[diamondالماس]].
 
When [[X-rays]] hit an [[atom]], they make the [[electron|electronic cloud]] move as does any [[electromagnetic wave]]. The [[Motion (physics)|movement]] of these [[electric charge|charges]] re-radiates [[waves]] with the same [[frequency]] (blurred slightly due to a variety of effects); this phenomenon is known as the [[Rayleigh scattering]] (or elastic scattering). The scattered waves can themselves be scattered but this secondary scattering is assumed to be negligible. A similar [[process]] occurs upon [[scattering]] neutron waves from the [[atomic nucleus|nuclei]] or by a [[coherent]] [[Spin (physics)|spin]] interaction with an unpaired [[electron]]. These re-emitted [[wave field]]s [[interfere]] with each other either constructively or destructively (overlapping waves either add together to produce stronger peaks or subtract from each other to some degree), producing a diffraction pattern on a detector or film. The resulting wave [[interference]] [[pattern]] is the basis of [[diffraction]] analysis. Both [[neutron]] and [[X-ray]] wavelengths are comparable with inter-atomic distances (~150&nbsp;[[1 E-12 m|pm]]) and thus are an excellent probe for this [[length scale]].