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A typical flashlight consists of a small electric lightbulb with associated parabolic reflector, powered by electric batteries, and with an electric power switch. The components are mounted in a housing that contains the necessary electric circuit and provides ease of handling, a means of access to the batteries for replacement, and a clear covering over the lightbulb for its protection.
Although a relatively simple device, its invention did not occur until the late 19th century because it depended upon the earlier invention of the electric battery and electric light. The batteries in the first ones were of such short useful life that the common method of operating them was to flash them just long enough to discern the environs, and only as needed; hence the term "flash-light".
Recently, flashlights which use light-emitting diodes (LEDs) instead of conventional lightbulbs have become available. LEDs are far more efficient than, and use less power than normal lightbulbs, and so torches which use them have longer battery lifetimes. Another innovation in flashlight design is the headlamp, a flashlight worn on the head for hands-free operation. Powerful headlamps mounted on helmets have been used in mining for decades, but general-purpose ones with fabric straps are now also available.
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 lanterns of the day, 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 candleThis article is on the source of light. For other meanings see Candle (disambiguation A candle is a light source usually consisting of an internal wick which rises through the center of a column of solid fuel. Typically the fuel is a form of wax with paras. It is possible that future developments of battery and LED technology will bring interesting new designs. For instance, one very small light that exists now in 20042004 is a leap year starting on Thursday (the link is to a full 2004 calendar), and has also been designated the: International Year of Rice International Year to Commemorate the Struggle against Slavery and its Abolition Elections are to be held in 73 co consists of a few LEDs with a switch, designed to be an endcap for a 9-volt battery .
You might think of a flashlight as a $20 item at maximum, but actually flashlights go for as much as several hundreds of dollars. Such flashlights are very advanced, using special batteries, have adjustable brightness levels, dive-depth waterproof ratings, interchangeable opticsSee also list of optical topics. Optics is a branch of physics that describes the behavior and properties of light and the interaction of light with matter. Optics explains and is illuminated by optical phenomena. The field of optics usually describes the, and are very bright.