refractive

Refractive refers to properties and phenomena related to refraction, the bending of light as it passes between media with different optical densities. The amount of bending depends on the refractive indices of the media and the angles of incidence and refraction, described by Snell's law: n1 sin theta1 = n2 sin theta2. The refractive index n of a medium is the ratio of the speed of light in vacuum to its speed in that medium.

Materials are characterized by their refractive index, a dimensionless quantity. Vacuum has an index of 1.0; air is about 1.0003; water ~1.333; common glasses range around 1.5 to 1.9; diamond is about 2.4. Light also travels at different speeds for different wavelengths in a given material, a property known as dispersion, which can cause chromatic separation and blur in optical systems.

Refractive effects are fundamental to many optical technologies. Lenses use refraction to bend light and form focused images in glasses, cameras, microscopes, and spectacles. In fiber optics, light is guided through cables by successive refractions and total internal reflection. Prisms, coatings, and various optical elements manipulate refraction to control glare, coloration, and focus. Dispersion and refractive corrections also lead to practical considerations such as chromatic aberration and anti-reflective coatings.

Measuring refractive properties is important in science and engineering. Refractive index is determined with refractometers and is used to identify materials and assess purity. Clinically, refractive concepts underpin the diagnosis and correction of refractive errors in the eye, where the cornea and lens bend light to form a clear image on the retina.