Brewster, Sir David (1781-1868), a Scottish scientist, is best known for the law named in his honor, Brewster’s law. This law relates the amount that light is polarized to the refractive index of the medium the light is passing through. Polarized light consists of light waves that have a simple, orderly arrangement. The refractive index of a medium equals the velocity (speed in a particular direction) of light in a vacuum divided by the velocity of light in the medium. The indexes of most kinds of glass are around 1.5 to 1.6. See Polarized light .
Brewster invented the kaleidoscope and an improved stereoscope, an optical viewing device that makes photographs seem to have three dimensions. Another of his inventions was a kind of lens that was later perfected by—and named in honor of—the French physicist Augustin J. Fresnel and used in lighthouses. Brewster also wrote Life of Sir Isaac Newton (1860).
Brewster was born on Dec. 11, 1781, in Jedburgh, Borders Region, Scotland, and was educated at Edinburgh. In 1815, he was elected a Fellow of the Royal Society, one of the world’s leading scientific organizations. He was knighted in 1832. He became principal of St. Andrews University in 1838 and principal of the University of Edinburgh in 1860. Brewster died on Feb. 10, 1868.
See also Kaleidoscope ; ; Stereoscope .
