Birefringence materials with positive dielectric anisotropy

For a nematic material with positive dielectric anisotropy, induced birefringence can also be observed. However, the liquid crystal must be in the uniform parallel orientation at zero volts.Above the threshold voltage, the director aligns itself parallel to the applied field. With crossed polarizer and analyzer, the voltage dependence of the light intensity is reversed from that described previously for a fluid of negative dielectric anisotropy. ... 

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