22.2. Optics http://www.ck12.org
FIGURE 22.12
The term “mirror image” refers to how
left and right are reversed in the image
compared with the real object.FIGURE 22.13
The image created by a concave mirror
depends on how far the object is from the
mirror.Convex Mirrors
The other type of curved mirror, aconvexmirror, is shaped like the outside of a bowl. This type of mirror forms
only virtual images. The image is always right-side up and smaller than the actual object, which makes the object
appear farther away than it really is. You can see how a convex mirror forms an image inFigure22.14 and in the
animation at the URL below. Because of their shape, convex mirrors can gather and reflect light from a wide area.
This is why they are used as side mirrors on cars. They give the driver a wider view of the area around the vehicle
than a plane mirror would.
http://physics.slss.ie/resources/convex%20mirror.swf
Refraction of Light
Although the speed of light is constant in a vacuum, light travels at different speeds in different kinds of matter. For
example, light travels more slowly in glass than in air. Therefore, when light passes from air to glass, it slows down.
If light strikes a sheet of glass straight on, or perpendicular to the glass, it slows down but passes straight through.
However, if light enters the glass at an angle other than 90°, the wave refracts, or bends. This is illustrated inFigure
22.15. How much light bends when it enters a new medium depends on how much it changes speed. The greater the
change in speed, the more light bends.