**Figure 3**
(*a*) *A* represents the incident wavefront, *S* the specular wavefront and *B* the wavefront at the scattering angle 2θ, which is drawn for the direction when the scattering from each plane is in phase. The Bragg equation assumes there is only one peak at the detector and this occurs when both *B* and *S* are coincident, *i.e.* the scattering is a mirror reflection, whereas the new explanation allows *B* and *S* to be separated. (*b*) This is a map of the number of scattering points with a path difference < 10^{−4} nm as a function of Ω and 2θ obtained with steps in α of 10^{−5} rad, plotted on a linear scale from 0 to 2000 scatters (see supporting information). The maximum is at 300 000 for the Bragg condition when all the contributions are in phase. |