When light separates into its component wavelengths, an observer perceives bands of colour due to the human eye’s sensitivity to different parts of the visible spectrum.
- When sunlight is dispersed by rain and forms a rainbow, an observer often distinguishes red, orange, yellow, green, blue and violet bands of colour.
- Although an atmospheric rainbow contains electromagnetic waves with all possible wavelengths between red and violet, our eyes encounter difficulties in distinguishing between colours within specific regions of this spectrum. For example, all wavelengths between 520 to 570 nanometers may appear to be exactly the same green to most observers.