Engineering Physics

3.7 Laue method

In Laue method, a narrow beam of white X-rays [usually in the wavelength range, 0.2 to 2.0 Å] is obtained by passing X-rays through a collimator ‘C’. This beam is allowed to fall on a stationary single crystal ‘S’ as shown in Fig. 3.13(a). The crystal act as a 3-dimensional diffraction grating to the incident beam. The processes of reflection of X-rays by crystal planes is considered as X-ray diffraction. The diffraction phenomenon satisfies Bragg’s law, nλ = 2d sin θ. where n = 1, 2, 3, … represent the order of diffraction, λ = wavelength of diffracted X-rays from a system of crystal planes with interplanar spacing ‘d’ and θ = glancing angle i.e., the angle made by X-rays with a crystal plane. As the crystal is not rotated, so, ...