These are perhaps the most fundamental interactions of light with matter, since they must often precede some of the other interactions described later. A good account of most of these will be found in the book by Slayter (1970). When light falls upon an object some of it will be reflected, some of it absorbed, and the remainder will be transmitted, phenomena which are familiar from everyday life, Most of the objects we observe are seen by the light that they reflect towards the eye, and their different surface appearances depend on the nature of this reflection. Some objects are transparent, enabling us to observe them by virtue of the light that they transmit - wine in a glass, church windows and colour transparencies are obvious examples.