The refractive index is the ratio of the light speed in a vacuum to the light speed in the medium. It is mainly used to describe the material's ability to refract light.

The material with higher refractive index, the ability to refract incident light is stronger.

In China, the standard of refractive glass beads for pavement GB/T24722-2009, according to the refractive index of glass beads, glass beads can be divided into three types: low refractive index glass beads, medium refractive index glass beads, and high refractive index glass beads, the refractive index (RI) is 1.50≤RI <1.70, 1.70≤RI <1.90, and RI≥1.90.

1.5 Refractive index glass beads: It is mainly made by crushing, sieving and melting recycled glass, the main component is silica.

1.7 Refractive Index Glass Beads: It adopt a matching method, first melting 1.7 refractive index glass, then furnacing glass beads.The main component is titanium dioxide, with a density of ≥3.0.The technical requirements and melting process are complicated, but the maximum retro reflective of 1.7 index glass beads can reach more than 1000mcd, and it has a good reflectivity in rainy night condition.Drop on the 1.7 beads on road without paint, it can reach about 200mcd.Particle size range: 0.212 ~ 2.0mm.

（1.7 index beadsdrop onthermoplastic paint with 2% Titanium, the reading is 582mcd）