LIQUID CRYSTAL ☺ A state exists between two temperature i.e. melting temperature and clearing temperature is called liquid crystal. ☺ Discovered by Austrian botanist Frederick Reinitzer in 1888. ☺ Optical properties of solid and fluidity of liquids are present in them. ☺ On the basis of nature of ordering of molecules liquid crystal are divided into !; Nematic. 2; Smectic 3; cholestric ☺ They have orientational order, but very weak or no positional order. These turbid liquid resembles in crystal in some optical properties. They have properties in between crystalline solids and liquids are called liquid crystal. ☺ Liquid crystal state exists between two temperatures i.e. melting temperature and clearing temperature. Crystal ------ liquid crystal ------- liquid ☺ All liquid crystals are organic and have elongated molecules, which end in a polar group. ☺ They are always isotropic. Applications:- Due to the optical and electrical properties, liquid crystals have many practical applications. Liquid crystals diffract light and impart colour. It change colour with change in temperature because they are sensitive to heat. (1) It is used to find out the point of potential failure in electrical circuit. (2) Room thermometer contains liquid crystal with suitable temperature range. (3) It is used in display of electrical device like digital watch, calculator and computers. (4) In chromatography it is used as solvent. (5) They are used in medicine to locate, veins arteries, infection, fracture and tumors.
Posted on: Sun, 21 Dec 2014 17:18:42 +0000
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