- Dispersion is the result of the relationship between refractive index and wavelength.
- Every wavelength of light is affected to a different degree by the refractive index of a material and as a result changes direction by a different amount when passing from one medium (such as air) to another (such as glass). As a result, in the case of white light, the separate wavelengths span out with red at one end and violet at the other
- Another familiar example of dispersion is when white light strikes raindrops and a rainbow of colours become visible to an observer.
- As the light first enters and then exits a droplet it separates into its component wavelengths which the observer perceives as colour.
- Colour is not a property of electromagnetic radiation, but a feature of visual perception by an observer.