Where Does "n" Index of Refraction Come From?

The index of refraction is a numerical representation of how much a material will slow the speed of light when traveling through it. The amount of reduction is based on a relationship between the speed of light in air and the speed of light in the given medium. A material with a higher index of refraction will slow the light more than a lower one. If the medium is in the form of a prism (a lens), not only will the light slow, it will also bend. The more the light is slowed when traveling through the prism, the more it will bend. With more bending, less material is required to achieve the desired result of focusing light on the retina. Less material translates into a lens with less thickness, which is cosmetically appealing to customers. The index of refraction, “n,” is based on a formula which divides the speed of light in air by the speed of light in a given medium. The speed of light in air is 186,000 miles per second. For the purposes of dispensing, all “n” (index) values are ...