ABSTRACT
Reflection and refraction form the basis of this discussion, which then expands to illustrate how these principles are used in the design of different luminaires.
Reflection Reflection is a physical principle by which light is bounced or reflected from a surface. The basic principle of reflection is governed by the Law of Reflection (Figure 7.1), which states that the angle of incidence is equal to the angle of reflection (when considering an angle that is normal or perpendicular to the surface of the object). In essence, this simply means that when light bounces off a surface, it does so at an angle that is complementary (or equal) to the angle at which it first struck the surface. Materials that have shiny mirrored surfaces create reflections that follow the Law of Reflection quite specifically, and we call these reflections specular reflections. Other materials don’t provide as good a surface for reflection and create either a spread reflection, where most of the light is reflected off the surface in the same general direction, or a diffuse reflection, where the light is scattered in numerous directions. A crumpled piece of aluminum foil can create spread reflections, while most objects that have an uneven surface or are made of un-mirrored materials characteristically produce diffuse reflections. In reality, most surfaces are associated with diffuse reflections.
