Definition

optical glass: Glass used in themanufacture of lenses, prisms, andother optical parts. It must be homogeneousand free from bubbles andstrain. Optical crown glass may containpotassium or barium in place ofthe sodium of ordinary crown glassand has a refractive index in therange 1.51 to 1.54. Flint glass containslead oxide and has a refractiveindex between 1.58 and 1.72. Higherrefractive indexes are obtained byadding lanthanoid oxides to glasses;these are now known as lanthanumcrowns and flints.