searchlight

Edison's classic searchlight cart.

Searchlights in action, Gibraltar 1940.

Use of searchlights at the Luminato arts festival in Toronto

Demonstrates the height of Tokyo Sky Tree before built in 2007

A searchlight is an apparatus that combines a bright light source with some form of curved reflector or other optics to projecting a powerful beam of light of approximately parallel rays in a particular direction, usually devised so that it can be swiveled about.

Military use of searchlights started late 19th century, when battleships and other major vessels were equipped for finding small attacking torpedoboats. They saw use in the Russo-Japanese War 1904 - 05. Searchlights were also installed on many coastal artillery batteries for aiding night combat.

In World War I

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.

In World War II

Searchlights were used extensively in defense 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 blinded bombardiers using optical bombsights.

Searchlights were occasionally used tactically in ground battles. One famous occasion was the Soviets' use of seachlights during the Battle of Berlin in April 1945. 143 searchlights were directed at the German defense force across the Neisse River with the aim of temporarily blinding them during a Soviet offensive. However, the morning fog diffused the light and silhouetted the attacking Soviet forces, making them clearly visible to the Germans. The Soviets suffered heavy losses as a result and were forced to delay their invasion of the city.

World War II-era searchlights include models manufactured by General Electric and by the Sperry Company, (of gyroscope fame). These were mostly of 60" (152.4 cm) diameter with rhodium plated parabolic mirror, reflecting a carbon arc discharge. Peak output was 800,000,000 candlepower. It was powered by a 15 KW generator and had an effective beam visibility of 28 to 35 miles (45 to 56 km) in clear low humidity.

Modern use

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, and Fox television network.

See also

• Mangin mirror
• Military applications of searchlight
  • Canal Defence Light
  • Turbinlite
  • G-numbers

References

• FM 4-29 seacoast searchlights
• FM 4-111
• FM 4-115

Notes

External links

Wikimedia Commons has media related to: Searchlights

• 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
• http://www.skylighters.org/mainmenu.html

v • d • e Lamps and lighting Incandescent Regular · Halogen · Parabolic aluminized reflector (PAR) · Nernst Fluorescent Fluorescent (Compact) · Fluorescent induction High-intensity discharge (HID) Mercury-vapor · Hydrargyrum medium-arc iodide (HMI) · Hydrargyrum quartz iodide (HQI) · Metal halide (Ceramic) · Sodium vapor Gas discharge Deuterium arc · Neon · Sulfur · Xenon arc / Xenon flash · Black light · Tanning lamp · Germicidal · Growth light Electric arc Carbon arc · Yablochkov candle Combustion Acetylene/Carbide · Argand · Candle · Diya · Gas · Kerosene · Lantern · Limelight · Oil · Safety · Rushlight · Tilley · Torch Other Light-emitting diode (LED) · Solid-state (SSL) · Plasma · Electroluminescent wire · Chemiluminescence · Radioluminescence · Glow stick