Key Concepts
What is the law of reflection?
What type of image is produced by each of the three types of mirrors?
Vocabulary
ray diagram
angle of incidence
angle of reflection
plane mirror
virtual image
concave mirror
focal point
real image
convex mirror
Reading Strategy
Comparing and Contrasting After reading this section, compare mirror types by copying and completing the table.
Mirror |
Shape of Surface |
Image (virtual, real, or both) |
---|---|---|
Plane |
Flat |
Virtual |
Concave |
a. |
b. |
Convex |
c. |
d. |
It is a bright, sunny day and you are enjoying a peaceful afternoon by a lake. The air is still and the surface of the lake looks just like a sheet of glass. In fact, it is so smooth that you can see your reflection in it.
Optics includes the study of how mirrors and lenses form images. In your study of optics, assume that light is made up of rays that travel in straight lines. A ray diagram shows how rays change direction when they strike mirrors and pass through lenses.
Figure 1 shows a simple ray diagram of the law of reflection. The incoming ray, called the incident ray, approaches the mirror. The angle of incidence is the angle the incident ray makes with a line drawn perpendicular to the surface of the mirror. The mirror reflects the incident ray. The angle of reflection is the angle the reflected ray makes with the perpendicular line. The law of reflection states that the angle of reflection is equal to the angle of incidence.
Figure 1 The flat (plane) mirror and the mirror-like lake surface both obey the law of reflection. According to the law of reflection, the angle of an incident ray equals the angle of the reflected ray.