20.1. Light as a Ray and the Law of Reflection http://www.ck12.org
FIGURE 20.2
The sun produces its own light but the moon shines by reflected sunlight.FIGURE 20.3
We usually think of light as traveling rays.The Law of Reflection
One of the simplest cases is true reflection on a flat mirror.Figure20.4 shows a diagram of two light rays reflecting
off a flat (plane) mirror. The dashed lineNis thenormalto the plane of the mirrorM. Theincident raysmake an
angleθiwith the normalN. Thereflected raysmake an angleθrwith the normal,N.
The Law of Reflection states:
The angle of incidence(θi)is equal to the angle of reflection(θr).
θi=θr