Fysici
Sir David Brewster (1781-1868) |
| Scottish
physicist noted for his experimental work in optics and polarized
light—i.e., light in which all waves lie in the same plane.
When light strikes a reflective surface at a certain angle (called
the polarizing angle), the reflected light becomes completely polarized.
Brewster discovered a simple mathematical relationship between the
polarizing angle and the refractive index of the reflective substance.
This law is useful in determining the refractive index of materials
that are opaque or available only in small samples. Brewster was educated
for the ministry at the University of Edinburgh, but his interest
in science deflected him from pursuing this profession. In 1799 he
began his investigations of light. His most important studies involved
polarization, metallic reflection, and light absorption. He was elected
a fellow of the Royal Society in 1815, and he invented the kaleidoscope
the following year. He was knighted in 1831. In the early 1840s he
improved the stereoscope by utilizing lenses to combine the two dissimilar
binocular pictures and produce the three-dimensional effect. Brewster
was instrumental in persuading the British to adopt the lightweight,
flat Fresnel lens for use
in lighthouses. In 1838 he became principal of the United College
of St. Salvator and St. Leonard of the University of St. Andrews and
in 1859 became principal of the University of Edinburgh. Of Brewster's
numerous published works, his Treatise on Optics (1831) and Memoirs
of the Life, Writings and Discoveries of Sir
Isaac Newton (1855) are probably the most important. © 1999-2001 Britannica.com Inc. |
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