Posted by: Prospector PJ24 OCT 2012
From fairy tale and superstition to science, the mirror has proved an important tool in both fantasy and reality. Pools of water probably acted as the first mirrors, but examples of obsidian mirrors found in Anatolia (modern day Turkey) have been dated to around 6000BC. Mystical powers have long been attributed to reflecting objects, and catoptromancy (the art of divination by mirrors) is just one technique employed by fortune tellers and mystics.
Catoptrics is the element of optics that deals with reflection. Euclid was one of many scientists to study this branch of science, when he wrote a book called ‘Catoptrics’ that covered the mathematical theory of mirrors. The mathematician Diocles investigated parabolic mirrors, and Ptolemy experimented with curved polished iron mirrors.
German chemist Justus von Liebig is credited with inventing the silvered-glass mirror in 1835. Von Liebig’s process involved the deposition of a thin layer of metallic silver onto glass through the chemical reduction of silver nitrate. Modern mirrors are often produced by the vacuum deposition of aluminium or silver directly onto glass.
The Italian town of Viganella made innovative use of an 8m x 5m computer controlled mirror in 2006. Due to its location in a steep-sided valley the town gets no direct sunlight for seven weeks each winter, so the mirror was installed to reflect sunlight into the town’s piazza.
Other types of reflecting device include acoustic mirrors, used to detect sound waves during the 1939–45 war, and corner reflectors, which use three flat mirrors to reflect light back to its source in an emergency. Hot mirrors reflect infrared light while allowing visible light to pass and can be used to reduce heating of components in optical devices.