Sometimes referred to as a converging mirror, the concave mirror is made with a surface that bends inward. Because the center of the curve is directed away from any incident light, it creates a reflection that is typically larger than the actual focal point.
This type of mirror is considered a converging device because it collects the light that falls into the bowl created by the inward bulge of the surface. This collection causes the light to refocus into a single focal length. The light is collected at different angles, since the concave nature of the bulge allows the light rays to make normal contact at differing depths at each point on the surface of the mirror.
The unique reflection that is created by a concave mirror makes the device extremely useful in a number of different devices. One of the most common applications is with the production of automobile headlights. By placing the source of light at the center of the mirror reflector, the result is a parallel beam of light that provides both good visibility for the driver of the car as well as points of light that are obvious to approaching vehicles.
In a similar way, the concave mirror provides a focused beam of light for searchlights. The construction of the lens allows the production of a parallel beam that can be easily directed when the searchlight is swiveled or positioned. Featuring a relatively easy construction, this mirror helps to keep the cost of the searchlights relatively low while still being one of the more durable components on the device.
The dental profession also benefits from the use of a concave mirror. It is used to focus light onto the area of the mouth that the dentist is working on, providing a clear reflection of the tooth or set of teeth. This type of mirror can be handheld or mounted over the dental chair.
A concave mirror can be very helpful around the house as well. Men may use one while shaving, since the device will provide a magnified image of the beard line. Women often use one while applying makeup for its magnifying properties as well, since the larger image can make detailed makeup much easier to apply.
Even the field of alternative energy benefits from this type of mirror. Solar heating devices often make use of concave mirror panels as a means of gathering solar energy for storage. The bowl-like design helps to collect the sun's rays and focus them into a battery system, proving to be much more efficient than some other methods of powering solar heating systems.