Underwater Strobe

Strobe light or stroboscopic lamp, commonly called a strobe, is a device used to produce regular flashes of light. It is one of a number of devices that can be used as a stroboscope. The word originated from the Greek strobos, meaning "act of whirling."

Strobe lights are used in scientific and industrial applications, in clubs where they are used to give an illusion of slow motion (cf. stroboscopic effect) and for aircraft anti-collision lighting. Other applications are in alarm systems, theatrical lighting (most notably to simulate lightning), and as high-visibility running lights. They are still widely used in law enforcement and other emergency vehicles, though they are slowly being replaced by LED technology in this application, as they themselves largely replaced halogen lighting. Strobes are used by scuba divers as an emergency signaling device.

Strobe lighting has also been used to see the movements of the vocal cords in slow motion during speech, a procedure known as video-stroboscopy. Special calibrated strobe lights, capable of flashing up to hundreds of times per second, are used in industry to stop the motion of rotating and other repetitively-operating machinery and to measure the rotation speeds or cycle times. Strobelights are often used in nightclubs and raves, and are available for home use for special effects or entertainment.
A strobe light flashing at the proper period can appear to freeze or reverse cyclical motion

A typical commercial strobe light has a flash energy in the region of 10 to 150 joules, and discharge times as short as a few milliseconds, often resulting in a flash power of several kilowatts. Larger strobe lights can be used in “continuous” mode, producing extremely intense illumination.

The light source is commonly a xenon flash lamp, which has a complex spectrum and a color temperature of approximately 5,600 kelvins. To obtain colored light, colored gels must be used.

The origin of strobe lighting dates to 1931, when Harold Eugene "Doc" Edgerton employed a flashing lamp to make an improved stroboscope for the study of moving objects, eventually resulting in dramatic photographs of objects such as bullets in flight.

EG&G [now a division of URS] was founded by Harold E. Edgerton, Kenneth J. Germeshausen and Herbert E. Grier in 1947 as Edgerton, Germeshausen and Grier, Inc. and today bears their initials. In 1931, Edgerton and Germeshausen had formed a partnership to study high-speed photographic and stroboscopic techniques and their applications. Grier joined them in 1934, and in 1947, EG&G was incorporated.

During World War II, the government's Manhattan Project made use of Edgerton's discoveries to photograph atomic explosions; it was a natural evolution that the company would support the Atomic Energy Commission in its weapons research and development after the war. This work for the Commission provided the historic foundation to the Company's present-day technology base.

The strobe light was popularized on the club scene during the 1960s when it was used to reproduce and enhance the effects of LSD trips. Ken Kesey used strobe lighting in coordination with the music of the Grateful Dead during his legendary Acid Tests.

Strobe lighting can trigger seizures in photosensitive epilepsy. An infamous event took place in 1997 in Japan when an episode of the Pokémon anime, Dennō Senshi Porygon, featured a scene that depicted a huge explosion using flashing red and blue lights, causing about 685 of the viewing children to be sent to hospitals. These flashes were extremely bright strobe lights.

Most strobe lights on sale to the public are factory-limited to about 10-12 flashes per second in their internal oscillators, although externally triggered strobe lights will often flash as frequently as possible. At a frequency of 10 Hz, 65% of affected people are still at risk. The British Health and Safety Executive recommend that a net flash rate for a bank of strobe lights does not exceed 5 flashes per second, at which only 5% of photosensitive epileptics are at risk. It also recommends that no strobing effect continue for more than 30 seconds due to the potential for discomfort and disorientation.

Reprinted from Wikipedia.org

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