 | Acta Crystallographica Section E Acta Crystallographica Section E CRYSTALLOGRAPHIC COMMUNICATIONS |
journal menu
![[Figure 1]](oi2029fig1mag.jpg)
|
|
Figure 1
Simplified geometric model to illustrate Bragg diffraction of parallel, monochromatic X-rays on the lattice planes {hkl} of a crystal. To generate an intensity maximum in the far field via constructive interference, the reflected wavelets that emerge from the two lattice planes at C and E, need to be in phase. According to the kinematic theory and the Born approximation, the two reflected waves are shifted by −π/2 with respect to the incident wavelets as shown (Cowley, 1975  ). Under the condition that the incident wavelets at A–B and C–D are in phase, this can only be achieved if the path difference D–E–F between the wavelet emerging from the bottom lattice plane at E and the wavelet from lattice plane at C is an integral multiple of the wavelength according to Equation (1). Note, that the Bragg angle θ appears not only as the glancing angle, but also in the two right-angled triangles cornered by C–D–E and C–E–F. Moreover, it is important to note that the opposite minor cathetus in these right-angled triangles has the length λ/2, which is one of the key parameters that is going to be changed within this teaching concept. |
![[Figure 1]](oi2029fig1.jpg)
| CRYSTALLOGRAPHIC COMMUNICATIONS |
ISSN: 2056-9890
Open 
access
access
