Optically Active Substances Page 234

Optically active substances are Materials that rotates the plane of incident plane polarized light is optically active. Optical rotation is the turning of the plane of linearly polarized light about the direction of motion as the light travels through certain materials. It occurs in solutions of molecules such as sugar, solids with rotated crystal planes such as quartz, and polarized gases of atoms or molecules. It is used in the sugar industry to measure syrup concentration, in optics to manipulate polarization, in chemistry to characterize substances in solution, and in optical mineralogy to help identify certain minerals in thin sections. It is being developed as a method to measure blood sugar concentration in diabetic people.

For further information on optical activity: tOptics/SugarSyrups/SugarSyrups.html tOptics/SugarSyrups/SugarSyrups.html

Liquid Crystal Displays LCD’s are made of arrays of pixels between crossed polaroids. When a voltage is applied across the electrodes, the resulting electric fields moves the liquid crystal molecules in the pixels. See: (13:58)