A Simple Method of Demonstrating Diffraction Grating Effects

A description is given of an apparatus with which Fraunhofer diffraction at very small angles can be observed. It provides a simple way of demonstrating diffraction by comparatively large objects and in particular the orders of diffraction from gratings of about 1 mm. spacing are well separated. On this scale it is possible to introduce faults into gratings to illustrate effects that could arise in practice. Several gratings are described and the diffraction patterns from them are discussed with reference to certain X-ray diffraction effects from transition structures in alloys.