Section 19.2 The Law of Reflection
Subsubsection Key Ideas
When a ray of light encounters an object, the light is usually either absorbed by the object or is reflected by the object. If it is reflected, it will continue moving in a straight line in a new direction given by the Law of Reflection. Objects like mirrors typically reflect most of the light that encounters them.
Principle 19.2.2. The Law of Reflection.
For a ray of light incident on a locally flat mirror, the reflected angle \(\theta_{r}\) is equal to the incident angle \(\theta_{i}\text{,}\) both measured from the line normal to the surface:
\begin{equation*}
\theta_{r} = \theta_{i}
\end{equation*}
Subsubsection Reflection Activities
Activity 19.2.1. Practice: Corner Reflector.
A corner reflector is made up of two mirrors meeting each other at a 90 degree angle. Let a light ray hit one of the mirrors so that the ray is reflected to the other mirror. Draw a ray diagram of this situation. What do you notice about the final reflected ray? What is special about this kind of object?
