REFLECTION AT A PLANE SURFACE

The figure shows how a ray of light is reflected by a plane surface. Let MM' represent a reflecting surface. When a ray of light is incident on MM' in the direction IO it gets reflected along the direction OR. IO is the incident ray; O is the point of incidence and OR is the reflected ray.

Reflection of a Ray Light by a Plane Mirror

Let ON be the normal drawn perpendicular to the surface MM' at the point of incidence. The angle which the incident ray makes with the normal at the point of incidence is called the angle of incidence and is denoted by the letter 'i'. The angle that the reflected ray makes with the normal at the point of incidence is called the angle of reflection 'r'. Mirror is an example of a reflecting surface.