No, brown is typically not seen in a natural rainbow.
Why Isn't Brown Visible in a Rainbow?
A rainbow is formed by the dispersion of sunlight as it passes through raindrops. The water droplets act like prisms, splitting white light into its constituent colours, which appear as a spectrum. This spectrum follows a specific order based on the wavelengths of light: Red, Orange, Yellow, Green, Blue, Indigo, and Violet (ROYGBIV).
Colours like brown are not fundamental spectral colours. Instead, they are often the result of mixing different colours or appear under specific lighting conditions that aren't met in the formation of a rainbow.
As the provided reference explains:
Brown, for instance, is a mix of red and green. But the red and green bands in the rainbow aren't next to each other, so we don't see them mix to make brown. The same is the case for many other colours that are mixtures - if the colour bands in the rainbow don't overlap then they can't mix.
In a rainbow, the colours appear in distinct bands. Because the red and green bands are separated by orange and yellow, they do not overlap in a way that would allow them to mix and create brown.
Understanding Rainbow Colours vs. Mixed Colours
- Rainbow Colours: These are the pure spectral colours visible when light is dispersed (Red, Orange, Yellow, Green, Blue, Indigo, Violet). They are seen in a specific order.
- Mixed Colours: Many colours we perceive in everyday life (like brown, pink, or gray) are combinations of these spectral colours or involve variations in lightness and darkness. Brown is often perceived as dark orange or dark red, or as a mix of colours like red and green, or red, yellow, and blue.
Since a rainbow shows the separated spectral colours and doesn't typically involve the conditions needed for these colours to mix or appear in varying shades of darkness, colours like brown are absent.
Common Colours in a Rainbow Spectrum
| Colour | Order in Rainbow |
|---|---|
| Red | 1 |
| Orange | 2 |
| Yellow | 3 |
| Green | 4 |
| Blue | 5 |
| Indigo | 6 |
| Violet | 7 |
This clear separation of colours is why brown, a colour formed by mixing others (like red and green), is not visible in a standard rainbow.
