A flashlight (usually called a torch outside North America) is a hand-held electric-powered light source. Usually the light source is a small incandescent lightbulb or light-emitting diode (LED). Typical flashlight designs consist of the light source mounted in a reflector, a lens to protect the light source and reflector, a battery or other power source, and a switch.
In addition to the general-purpose hand-held flashlight, many forms have been adapted for special uses. Head or helmet-mounted flashlights designed for miners and campers leave the hands free. Some flashlights can be used underwater or in flammable atmospheres.
AccessoriesTranslucent, colored plastic cones slipped over the lens of a flashlight increase the visibility when looking at the side of the light. Such marshalling wands are frequently used for directing automobiles or aircraft at night.
Colored lenses placed over the end of the flashlight are used for signalling, for example, in railway yards. Colored light is occasionally useful for hunters tracking wounded game after dusk, or for forensic examination of an area.
Other designsA penlight is a small, pen-sized flashlight, usually containing two AA batteries or AAA batteries. In some an incandescent light bulb has an integral lens that focuses the light, thus no reflector is built into the penlight. Others use incandescent bulbs mounted in reflectors, while LED lamps are becoming increasingly common. Low-cost units may be disposable with no provision for the user to replace batteries or bulbs, and are sometimes imprinted with advertising for promotional purposes.
A headlamp is a flashlight designed to be worn on the head. A headlamp usually consists of the light emitter at the front, with a battery pack also attached to the front or back. The battery pack may be attached to the back of the head or in a pocket to improve balance. Headlamps leave the user's hands free, making them popular for recreational and occupational activities.
Sometimes a tactical light is mounted to a handgun or rifle. Such lamps are designed to withstand the impact of recoil, and to be easily controlled while holding the weapon.
Although most flashlights are designed for user replacement of the batteries and the bulb as needed, fully sealed disposable flashlights, such as inexpensive keyring lights, are made. When the batteries are depleted or the bulb fails, the entire product usually is thrown away or recycled and a new one purchased to replace it.
Diving lamps must be watertight under pressure and are used for night diving and supplemental illumination where surface light cannot reach.
People working in areas with significant concentrations of flammable gases or dusts, such as mines, engine rooms of ships, chemical plants or grain elevators, use so-called "non-incendive", or "explosion proof" flashlights. These are constructed so that any gas or dust that leaks into the flashlight is not likely to set off an explosion outside the light. The flashlight may require approval by an authority for the particular service and particular gases expected. The external temperature rise of the flashlight must not exceed the autoignition point of the gas, so substitution of more powerful lamps or batteries may void the approval.
Most flashlights are cylindrical in design, with the lamp assembly attached to one end. However, early designs came in a variety of shapes. Many resembled modern day lanterns, consisting largely of a box with a handle and the lamp attached to the front. Some others were made to have a similar appearance to candles. Portable hand-held electric lanterns can provide larger reflectors, lamps, and batteries than tubular flashlights meant to fit in a pocket. They are often designed for lighting the broad area immediately around the lantern, as opposed to forming a narrow beam; they can be set down on a level surface or attached to supports. Some electric lanterns use miniature fluorescent lamps for higher efficacy than incandesent bulbs.
Flashlights may be temporarily mounted on handlebars for bicycle lighting, although permanently mounted bicycle lamps are common.
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