How big is a rainbow?

When listener Sakura’s husband came home from his morning walk in Cambridgeshire, UK, he told her about a massive rainbow he’d seen. But when he showed her a picture, she didn’t think it was particularly large. So how big is a rainbow really? Are they always the same size? And if some are bigger than others, is there a limit?

To find the answers, presenter Marnie Chesterton meets independent rainbow expert Philip Laven in a pitch-black studio to simulate how a rainbow is formed. He demonstrates how they are created by sunlight, reflec...