Both concave and convex mirrors reflect light. However, one curves inward while the other curves outward. These mirrors also reflect images and light differently because of the placement of their focal points.
The principal axis is an imaginary line that cuts through the center of a mirror dividing it symmetrically in half. Imagine this as a curve on a piece of paper.
The focal point is a spot on the principal axis where light would intersect if it were to strike the mirror parallel to the principal axis.
Concave mirrors curve inward, creating a focal point in front of the mirror. Convex mirrors curve outward creating a focal point behind the mirror.
Because of their shape and focal point placement, images in concave mirrors appear upside down and far away. However, when you move closer, the object enlarges. If you get close enough, the object enlarges more and the image is right-side up.
In a convex mirror, images appear right-side up, shrunken and virtual, or placed somewhere behind the mirror.
- Image by Flickr.com, courtesy of Sarah