1. Scope 1.1 This guide covers the determination of refractive index of glass spheres used in pavement marking systems using a laser beam and a precision distance measurement device to calculate angle of reflection. This angle can then be used in a formula to calculate refractive index. 1.2 This guide provides for the presentation of refractive index of glass spheres to the requirement of the agency pavement marking material specification. sieve sizes. 1.3 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard. 1.4 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.
KeywordsIndex of Refraction, height gauge, laser
For many years, the only practical method of determining refractive index of glass spheres was with the use of refractive immersion oils. This method suffers from a number of drawbacks. 1. It is subjective requiring a visual judgemental observation of the human eye. 2. Immersion oils are expensive. Further, quite a number of them have been discontinued in production due to scarcity of available materials or toxicity. 3. At best immersion oils measure refractive index down to increments of .002. Further, measurement over the expected range of indices of glass spheres would require more than 100 immersion oils, not only expensive, but time consuming. 4. The proposed test method in this standard measures refractive index infinitely variable to 3 decimal places and can be performed in a matter of minutes.
The title and scope are in draft form and are under development within this ASTM Committee.Back to Top
Draft Under Development