The refractive index is a fundamental concept in optics and physics. It measures how much a beam of light slows down and bends when it enters a different medium. Mathematically, the refractive index \(n \) is defined as: \[n = \frac{c}{v} \], where \(c \) is the speed of light in a vacuum, and \(v \) is the speed of light in the medium. Because the refractive index of any substance is always greater than 1, this means light will always travel slower in a medium compared to a vacuum. For example:
- \( n \) of air is approximately 1.0003 \ (almost the same as vacuum)
- \( n \) of water is about 1.33 \ (light slows down more)
- Glass can have \( n \) values ranging from 1.5 to 1.9 depending on its type \ (light slows down even more)
. This slowing effect results in phenomena like refraction, where light bends as it passes from one medium to another.