A ghostly version of a rainbow

October has begun, and spooky season is here. So much so, even rainbows are playing dress-up and appearing as ghostly white.

Several fogbows were reported along the east coast of England over the weekend, including in this picture from Burnham Overy.

Despite looking just like rainbows, fogbows lack the distinctive seven colors.

The phenomenon occurs when sunlight interacts with tiny water droplets suspended in the air contained in fog, mist, and low clouds.

In contrast to rainbows, the water droplets that make up these so-called fogbows are much smaller, measuring 0.1mm across.

Rainbows are formed when sunlight enters raindrops and splits into seven colours as it travels through the water. This is called refraction.

The light is then reflected from the back of a raindrop and sent to your eyes. Hence for you to see a rainbow, the sun has to be behind you.

There is a similar, though slightly different process that occurs in a fog bow. Due to the smaller size of the water droplets, sunlight is diffracted before reaching your eyes.

The bow appears white and drained of color as a result. Because of this, fogbows are sometimes referred to as "white rainbows".

When light diffraction happens, it spreads out much more than when it refracts. Consequently, the bow turns an eerie white because the colors are washed out.

In order to see a fogbow, the fog needs to be quite thin.

From an aircraft, you can also see a similar atmospheric optical phenomenon called a cloud bow.