Rainbows and bridges

The weather on our return to Tattenhall Marina along the Shroppie back in October was a mix of sunshine and heavy showers. Perfect conditions for perfect rainbows.


My camera, sadly, is less than perfect, and couldn't do justice to the scene. Apart from the angle of view being not wide enough to capture the whole rainbow, you can see a splodge on the right where a lump of debris sits inside the lens assembly.


It's not just an optical illusion is it? The sky really is darker outside the rainbow. But why? After looking at a couple of websites I think this is the reason: the light we see inside the rainbow is a combination of the light directly from the sky and the light (from the sun) which has been refracted and internally reflected within the raindrops. The light we see outside the rainbow is just the light from the sky, with no extra reflected light. Please tell me if this is right or wrong!