ABSTRACT
Diffraction is used to identify unknown solids and molecules, but today both electrons and neutrons are used as well as X-rays to investigate the widest possible range of solids. The particle nature of phonons means they can be considered to “move” through solids, and many properties of solids that are affected by temperature can be explained in terms of phonons being scattered. The thermal properties of materials are an important consideration when designing objects ranging from buildings and bridges to computer chips. The propagation of electromagnetic radiation, in other words the way in which e-m radiation travels along, affects many areas of physics. When a beam of light—or indeed any other form of electromagnetic radiation—passes through a hole or slit, or round the outside of an object, it breaks up into a number of smaller beams.
