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Pop Quiz: September 2006

Test your knowledge of liquid crystals.

  1. “Liquid crystal” describes the state of matter between a melting point and a boiling point.
  2. Liquid crystals are used for electronic display systems because of the unique way they reflect light.
  3. Soapy water and “mood rings” are examples of different types of liquid crystals.
  4. The two phases of a liquid crystal are “positive” and “negative.”


  1. In 1888, an Austrian chemist conducted experiments on a substance to determine its melting point, and found that the substance appeared to have two melting points. At 145.5 degrees Celsius, the substance melted into a cloudy liquid, which existed until 178.5 degrees Celsius, where the cloudiness suddenly disappeared, giving way to a transparent liquid. Eventually the scientist realized that the cloudy liquid was a new state of matter, and coined the name “liquid crystal,” to illustrate that it shared important properties of both a liquid and a solid.
  2. Liquid crystals are “birefringent,” meaning that they possess two different indices of refraction. One index of refraction corresponds to light polarized along the director of the liquid crystal, and the other corresponds to light that's polarized perpendicular to the director.
  3. “Lytropic” (reacts with a solvent) liquid crystals are used to manufacture soap, and mood rings are “thermotropic” (temperature-sensitive) liquid crystals.
  4. The two main phases of liquid crystals are the “Nematic Phase” and the “Smectic Phase.” The Nematic Phase is similar to the liquid phase; the molecules float around like they do in a liquid phase, but still maintain a stable orientation. The Smectic Phase is similar to the solid phase.



In the August issue's New Products section, the Biamp NEXIA TC was incorrectly identified. The product is a digital signal processor targeted for use in teleconferencing applications.

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