A ghostly rainbow formed entirely out of fog descended over Lake Fairfax on Monday as a dense fog advisory blanketed most of the region.
Rainbows form when lights enters a water droplet. Each beam of sunlight travels at a different speed, slowing down at different rates when hitting a raindrop. Light is refracted and cast into an arc of color.
Fogbows, however, form from extremely small droplets, resulting in less refraction.
— Rob Gates (@rjgatesontheweb) November 9, 2020