The refractive index of a material is a measure of how much light slows down when it passes through that material compared to when it travels in a vacuum.
It tells us how much the path of light bends or refracts as it moves from one medium to another (like from air to glass or water). A higher refractive index means light slows down more and bends more sharply.
For example:
- The refractive index of vacuum is exactly 1.
- For air, it is slightly more than 1 (about 1.0003).
- For water, it’s around 1.33.
- For glass, it’s typically between 1.5 and 1.9.
This property is essential in optics and is used in lenses, glasses, cameras, fiber optics, and many scientific instruments.