# Converging Mirrors

## The Law of Reflection and Curved Surfaces

The Law of Reflection works for a curved surface just as it does for a flat surface:

• First, construct the normal to the surface where the ray strikes it (just imagine that there is a short plane mirror at that location, as in section 1, and draw a normal to it)
• Then measure the angle of incidence
• Now construct the angle of reflection equal to the angle of incidence on the other side of the normal.

## The Law of Reflection and Converging Mirrors

With a converging mirror, however, the Law of Reflection has a three of convenient side effects that make drawing ray diagrams for converging mirrors very quick and easy:

1. If a ray traveling parallel to the axis of the mirror strikes the mirror, it will be reflected (thanks to the Law of Reflection) through the focus of the mirror.
2. If a ray passing through the focus of the mirror strikes the concave mirror, it will be reflected (thanks to the Law of Reflection) parallel to the axis of the mirror.
3. If a ray of light passes through the center of curvature of the miror, it will be reflected back through the center of curvature.

These three ideas are all that you need to know to easily and conveniently locate the images formed by a concave mirror.