Searchlight
From Wikipedia, the free encyclopedia
- For other uses of searchlight see Searchlight (disambiguation).
A searchlight is an apparatus with reflectors for projecting a powerful beam of light of approximately parallel rays in a particular direction, usually devised so that it can be swiveled about.
Searchlights were first used in World War I to create "artificial moonlight" to enhance opportunities for night attacks, a practice which continued in World War II. Artificial moonlight was invented by historian and tank warfare theorist, Gen. J.F.C. Fuller.
Searchlights were used extensively in defence against nighttime aerial bomber raids around the time of World War II. In particular, pairs of searchlights spaced a known distance apart were used to determine (via triangulation) the altitude of enemy bombers, so that the fuses on anti-aircraft flak shells could be set appropriately for maximum effect. In addition, the lights may have helped blind bombardiers using optical bombsights.
Searchlights were occasionally used tactically in ground battles. One famous occasion was the Soviet's use of seachlights during the Battle of Berlin in April 1945. 143 searchlights, aimed to blind Nazi General Henrici's defense force across the Neisse River, failed as the morning fog diffused the light and made silhouettes of the attacking Soviet 1BF. The deeply entrenched Nazi army, muddy terrain, and spotlight mishap combined to cause large Soviet losses and a delayed penetration of the city.
World War II searchlights include the General Electric 1942-A Searchlight. This was a 60" (152.4 cm) in diameter lamp producing 800,000,000 candela. It was powered by a 15 KW generator and had an effective beam visibility of 28 to 35 miles (45 to 56 km).[1]
Today, searchlights are used in advertising, for instance by automobile dealers; the beam of light is visible over a large area, and (at least in theory) interested persons can find the dealer or store by following the beam to its source. This was once common for movie premieres; the waving searchlight beams still can be seen as a design element in the logo of the 20th Century Fox movie studio.
[edit] See also
- Military applications of searchlight
| Incandescent: | Conventional - Halogen - Parabolic aluminized reflector (PAR) |  |
| Fluorescent: | Compact fluorescent (CFL) - Linear fluorescent - Induction lamp | |
| Gas discharge: | High-intensity discharge (HID) - Mercury-vapor - Metal-halide - Neon - Sodium vapor | |
| Electric arc: | Arc lamp - HMI - Xenon arc - Yablochkov candle | |
| Combustion: | Acetylene/Carbide - Candle - Gas lighting - Kerosene lamp - Limelight - Oil lamp - Safety lamp - Petromax | |
| Other types: | Sulfur lamp - Light-emitting diode (LED) - LED lamp (SSL) - Fiber optics - Plasma - Electroluminescent wire | |
[edit] Notes
[edit] External links
- Sperry searchlight restoration project
- Elmer A. Sperry case file at the Franklin Institute archive of historical records of his consideration for a Franklin award in 1920 due to his invention of an electric searchlight
