Iceland Rainbows ~ Bill Belko caught this double bow produced by a low Icelandic sun. His shadow, marking the antisolar point, is visible at the bow centres.  ©Bill Belko, shown with permission.

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zero order glow                                   primary                                     secondary
The image shows many aspects of rainbows not to mention that photographing them involves getting wet.   The inner and brighter primary bow is from a single reflection inside the raindrops.   Its light forms a disk brightening the sky inside, we see colours only at its edge where the disks of different wavelength no longer overlap.     Light reflected twice forms the reversed coloured outer secondary bow and slightly brightens the sky outside.     No light enters the gap between the bows leaving the sky there dark ~ Alexander’s dark band.