In the last ten years, there have been many advances in applied optics, side by side with a considerable improvement in optical instruments. This progress has been mainly due to the application of electrical methods of detection of radiation, and in part to advances in other fields of physics. Optical methods have been increasingly introduced into industry, for control as well as for measurement. Where visible radiation is concerned, the improvement is in convenience rather than in sensitivity.Necessarily the selection of examples is arbitrary, but it is sufficiently diverse to illustrate the breadth of application of optics and the considerable progress which has been made.