Here’s how different colors of light travel at different speeds in a dispersive medium:
- Light is made up of different colors, each with a different wavelength (and frequency).
- When light enters a dispersive medium (like glass or water), its speed depends on the wavelength of the light.
- This happens because the medium’s refractive index varies with wavelength—a property called dispersion.
- Shorter wavelengths (like blue/violet light) are slowed down more than longer wavelengths (like red light) in the medium.
- As a result, blue light travels slower inside the medium than red light.
- This difference in speed causes the light to spread out into its component colors when passing through something like a prism.
- Physically, this happens because the light waves interact differently with the atoms in the material, depending on their wavelength.
So, the key is: the refractive index is wavelength-dependent, causing different colors to travel at different speeds in dispersive media. This effect is what creates phenomena like rainbows and the splitting of white light in prisms.