Aukje Borkent (Member 63,242) spotted a rare reflection bow while cycling with her boyfriend one afternoon near Den Hoorn, on the island of Texel, Netherlands. This is the faint bow that extends vertically from where the primary rainbow touches the horizon. Normal rainbows, like the primary one here, form as direct sunlight shines from behind you onto a sheet of rain up ahead. A reflection rainbow like Aukje’s appears at a different angle because it’s made of sunlight that shines from a different angle. And that is explained by what was behind Aukje and her boyfriend.

The light forming the reflection bow would have been reflecting off a still body of water behind them – likely IJsselmeer, a large lake inland from Texel. The water must have been still, forming a reflection that would have been like a second Sun shining up from below the horizon to form a fainter rainbow at a different angle. We are pleased to report to Aukje and her boyfriend that the optics decree that a primary rainbow and its reflection rainbow will always, without fail, come together at the horizon.