Refractive index is a measure of how much light slows down when it passes through a medium compared to its speed in a vacuum. It indicates how much the path of light bends, or refracts, when entering a material.
Relationship with Speed of Light:
- Light travels fastest in a vacuum, at approximately 299,792 kilometers per second.
- When light enters a medium like water, glass, or air, it slows down.
- The refractive index (n) is defined as: n = (speed of light in vacuum) / (speed of light in the medium)
- For example, if light travels at 200,000 km/s in glass, the refractive index of that glass would be: n = 299,792 / 200,000 ≈ 1.5
Key Points:
- n = 1 for vacuum.
- n > 1 for all other transparent materials.
- The higher the refractive index, the slower light moves through the material.
- It also affects how much the light bends at the boundary between two media.
Thus, the refractive index directly tells us how much the speed of light is reduced in a given material.