Brewster (B)
Brewster (B) : A unit used in optics to measure stress-induced birefringence. A material exhibits birefringence if it has different indices of refraction along different axes. Many crystals exhibit birefringence. In addition, certain substances, including many plastics, exhibit birefringence if they are subjected to compression or stress in one direction. The brewster, which measures this effect, has dimensions reciprocal to those of stress. One brewster is defined to equal 10-12?square meters per newton (m2/N) or 10-13?square centimeters per dyne (cm2/dyn). The unit is named for the British physicist David Brewster (1781-1868), who discovered stress-induced birefringence in 1816
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