How Diffraction Works: Bragg's LawX-rays ofwavelengthlQQQSimilar principleto multiple slit experiments Constructive and destructive interference patternsdepend on lattice spacing and wavelength of radiationBy varying wavelength and observing diffractionpatterns, information about lattice spacing is obtained
nl=2dsin(Q) • Similar principle to multiple slit experiments • Constructive and destructive interference patterns depend on lattice spacing and wavelength of radiation • By varying wavelength and observing diffraction patterns, information about lattice spacing is obtained How Diffraction Works: Bragg’s Law d Q Q Q X-rays of wavelength l l
DestructiveConstructiveInterferenceInterferenceED(hkl)(hkl)(hkl)
X-ray sourceX-ray detectorIncidentX-raysReflectedX-raysA0ed-BDCdsinedsineDifference inpath length =BC+ CDBC = CD = dhk/SinOnkDifference in path length = 2dnkisinonklMustbeanintegral numberofWavelengths, n = 2dhk/sinehkl(n = 1, 2, 3, ...)入 = 2dhkisineBragg Equation
x-raydetectormonochromator20-Hcrystal(being rotatedinto diffr. conditions)x-raysfrom generator
(111)1002=0.1542 nm (CuK-radiation)80(see)60(200)40(311)(220)20(222)(331) (420)(400)0502030406070809010011012020 (degrees)