Laws of Reflection. - When a beam of light, travelling in a homogeneous medium, comes to a second medium, some of the light is reflected. At a polished or silvered surface, nearly all the light is reflected. At the surface of clear glass, only a small part of it is reflected. The greater part of it enters the glass and passes through. In Fig, 37, let AB represent the reflecting surface, MP the perpendicular or normal to this surface, OP the incident ray, and PN the reflected ray. The angle OPM between the incident ray and the normal to the surface is called the angle of incidence. The angle MPN between the reflected ray and the normal to the surface is called the angle of reflection. Reflection at such a surface occurs according to the following two laws:
1. First law of Reflection. The incident ray, the reflected ray, and the normal to the surface lie in the same plane.
2. Second law of Reflection. The angle of incidence is equal to the angle of reflection.
Figure 37 - Reflection of light from a plane mirror. The angle