What does the index of refraction represent?

The index of refraction quantifies how much light slows down and bends as it passes from one medium into another. Specifically, it is defined as the ratio of the speed of light in a vacuum to the speed of light in the medium. This ratio indicates how much light is refracted and provides insight into the optical properties of the material.

For example, an index of refraction greater than 1 means that light travels slower in that medium than in a vacuum, leading to a bending of light at the interface between the two different media. This bending is what enables lenses to focus light and is fundamental to understanding how optical systems function.

In contrast, while factors like light intensity and the measure of bending power in a vacuum are important concepts in optics, they do not directly define the index of refraction. The index itself is solely concerned with the relationship between the speed of light in a vacuum and that in the medium, making it a crucial parameter in the study of optics and light behavior. Understanding this concept is essential for applications ranging from lens design to fiber optics.