NEN ISO 489 : 1984

Defines two methods for determining the refractive index of transparent plastics. Method A: Refractometric method for measuring the refractive index of transparent cast, moulded or sheet materials by means of a refractometer. The method is recommended when great accuracy is required. It is not applicable to powdered or granulated transparent materials. Method B: Immersion method (Becke line phenomenon) for determining the refractive index of powered or granulated transparent materials by means of a microscope and making use of the Becke line phenomenon.