The refractive index of a material depends on the wavelength of light — this phenomenon is known as dispersion.
Key Idea:
- Refractive index varies with wavelength: Light of different colors (wavelengths) travels at slightly different speeds in a medium, causing them to bend by different amounts.
- Generally, shorter wavelengths (like blue or violet light) have a higher refractive index, so they slow down more and bend more.
- Longer wavelengths (like red light) have a lower refractive index, so they bend less.
Example:
In glass:
- Blue light bends more than red light when entering or leaving the material.
- This leads to the splitting of white light into a spectrum (as seen in a prism or rainbow).
Why this happens:
- The interaction of light with the material’s atoms depends on the light’s frequency (which is inversely related to wavelength).
- Different wavelengths are affected differently, causing a spread of colors — the basis of chromatic effects in optics.