When a ray of light strikes a plane mirror, the light ray reflects off the mirror. Reflection involves a change in direction of the light ray. The convention used to express the direction of a light ray is to indicate the angle which the light ray makes with a normal line drawn to the surface of the mirror. The angle of incidence is the angle between this normal line and the incident ray; the angle of reflection is the angle between this normal line and the reflected ray. According to the law of reflection, the angle of incidence equals the angle of reflection. These concepts are illustrated in the animation below.
For more information on the ray nature of light, visit The Physics Classroom. Detailed information is available there on the following topics:
The Role of Light to Sight
The Line of Sight
The Law of Reflection
Why is an Image Formed?
Image Characteristics for Plane Mirrors
Ray Diagrams for Plane Mirrors
Other animations can be seen at the Multimedia Physics Studios.
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