Light waves spread out in all directions from a light source. When these light waves strike a smooth surface, they can be reflected to form images. A mirror is a smooth surface that reflects light in a way that allows images to be seen.

There are three main types of mirrors: plane mirrors, concave mirrors, and convex mirrors.  A plane mirror is flat and smooth. When you look into a plane mirror, your reflection appears upright and the same size as you. Bathrooms and bedroom mirrors are common examples of plane mirrors.  Unlike a plane mirror, a concave mirror curves inward. The type of image formed by a concave mirror depends on the object’s location relative to the focal point, which is the point where reflected light rays meet. The focal length is the distance from the center of the mirror to the focal point. Concave mirrors can make objects appear larger, smaller, upright, or inverted depending on how far the object is from the mirror. Because they can focus light, concave mirrors are often used in telescopes, flashlights, and makeup mirrors.  A convex mirror curves outward. When light rays strike a convex mirror, they spread apart after reflection. As a result, the image formed is always upright and smaller than the actual object. In addition, objects seen in a convex mirror appear farther away than they really are. Convex mirrors are commonly used as side mirrors on vehicles because they allow drivers to see a wider area.

Mirrors can also create two types of images: virtual and real. A virtual image cannot be focused onto a surface or screen. Plane mirrors and convex mirrors always produce virtual images. In contrast, a real image can be focused onto a surface because the reflected light rays actually meet. Concave mirrors can produce real images under certain conditions because of their curved surfaces and their ability to focus light.

Review:

1. Define mirror.
2. Identify the three types of mirrors.
3. What’s the difference between a real and a virtual image?