Refraction refers to the bending of light as it passes through a medium with a different refractive index. The refractive index of a material is a measure of how much the speed of light changes when it passes through the material. When light passes from one medium to another with a different refractive index, the angle of the light changes, causing the light to bend.
Pearlescent pigments are a type of pigment that can produce iridescent or pearlescent effects in coatings, plastics, and other materials. These pigments are typically made from mica coated with a layer of metal oxide, such as titanium dioxide or iron oxide. When light hits the pigment, it is reflected and refracted by the metal oxide layer, producing a range of colors and effects depending on the angle of observation and the thickness of the metal oxide layer.
The refractive properties of pearlescent pigments are key to their ability to produce these effects. As light passes through the metal oxide layer, it is refracted and bent in different directions, producing the iridescent and pearlescent colors that are characteristic of these pigments. The thickness of the metal oxide layer can be controlled to produce different colors and effects, and the angle of observation can also affect the appearance of the pigment.