The relationship between refractive index and dispersion lies in the fact that the refractive index of a material varies with the wavelength (or color) of light. This variation is the root cause of dispersion.
Key Points:
- Refractive Index Depends on Wavelength:
The refractive index is higher for shorter wavelengths (like violet and blue) and lower for longer wavelengths (like red).
This means violet light bends more than red light when entering or exiting a medium. - Dispersion Occurs Due to This Variation:
Because different wavelengths of light are refracted by different amounts, they spread out into a spectrum — this is dispersion. - Greater Variation = Greater Dispersion:
Materials where the refractive index changes sharply with wavelength (like flint glass) show more dispersion than those where the change is small (like crown glass). - Chromatic Dispersion:
This phenomenon is also known as chromatic dispersion, and it’s important in optics, lenses, and fiber communication, where different colors can focus or travel differently.