In the early days of diffraction fine details were not observable because the detectors were inefficient, and the sources were also of low intensities. Hence Bragg's law was the only type of diffraction observable, and Duane's approach could model it. Modern electron microscopes and x-ray diffraction instruments are many orders of magnitude brighter, so many find details of electron and x-ray diffraction are now known which cannot be explained by his approach. Hence his approach is no longer used.