Cavan Images/Alamy
Why, when I see a rainbow, do I perceive two extra colours (yellowish and greenish) directly beneath violet? Am I seeing UV wavelengths, with my brain interpreting them as those colours?
Guy Cox
Sydney, Australia
Your correspondent isn’t seeing in the ultraviolet range. Instead, they are seeing a supernumerary rainbow. This is caused by diffraction and interference after the initial refraction of sunlight by raindrops, and tends to happen when the drops are very small.
It is very difficult to photograph (believe me, I have tried).
Nick Canning
Coleraine, County Londonderry, UK
Rainbows sometimes show extra coloured bands directly…
