When you think of rainbows, you think of the seven-coloured band that hugs the sky.

 

But chances are you’ve probably never heard of a white rainbow. 

 

This spectacularly rare white rainbow was taken by photographer Melvin Nicholson while he was out on a shoot. This image was taken at Rannoch Moor in the west of Scotland.

 

A white rainbow is a natural phenomena caused by fog. This is why it also referred to as a fog bow.  “A fogbow is a "rainbow that has a white band that appears in fog and is fringed with red on the outside and blue on the inside," the National Weather Service told ABC News.

 

It appears white because of the water droplets are much tinier than your average rain drop.  According to  NASA,  “The fogbow's lack of colours is caused by the smaller water drops ... so small that the wavelength of light becomes important. Diffraction smears out colours that would be created by larger rainbow water drops.”

 

 

 

Nicholson told The Mirror, "It is a colourless rainbow that is made up of tiny water droplets that cause fog,” and that, “It's an amazing thing to witness and can generally only be seen if the sun is behind you when you are looking at it."