The refractive index of a transparent medium primarily decreases with an increase in wavelength of light. This fundamental relationship explains why different colors of light bend at slightly different angles when passing through materials like glass or water.
The Relationship: Refractive Index and Wavelength
In most transparent materials, the refractive index (often denoted by n) is not a constant value but varies depending on the wavelength (λ) of the light passing through it. This phenomenon is known as dispersion.
As the reference states, the refractive index of a medium decreases with an increase in wavelength of light. Conversely, this means that the refractive index increases as the wavelength decreases.
Wavelength and Color
Visible light is made up of a spectrum of colors, each corresponding to a different wavelength. Red light has the longest wavelength in the visible spectrum, while violet light has the shortest. The other colors (orange, yellow, green, blue, indigo) fall in between these two extremes.
Examples: Violet vs. Red Light
Applying the principle that refractive index decreases with increasing wavelength, we can understand how different colors are affected.
- Violet light, having the least wavelength, experiences a greater refractive index.
- Red light, having the greatest wavelength, experiences a smaller refractive index.
Therefore, as highlighted in the reference, the refractive index of a medium for violet light (least wavelength) is greater than that for red light (greatest wavelength).
Illustrating the Dependence
This table summarizes the relationship for visible light:
| Color | Relative Wavelength | Relative Refractive Index |
|---|---|---|
| Violet | Shortest | Highest |
| Indigo | Shorter | Higher |
| Blue | Medium | Medium |
| Green | Medium | Medium |
| Yellow | Medium | Medium |
| Orange | Longer | Lower |
| Red | Longest | Lowest |
This dependence on wavelength is why prisms separate white light into its constituent colors – each color (wavelength) is refracted at a slightly different angle due to the varying refractive index of the prism material.
