Asked by: Charlie Mack, Uckfield
A lot of things can glow in the dark, including your washing powder and of course those funky stars you stick on a child’s bedroom ceiling. They work through phenomena called phosphorescence and fluorescence. The material absorbs energy (usually in the form of a particular colour light) and then releases it as another colour light.
Fluorescent materials do this all at once, so when you shine UV light (from a torch or the Sun) on washing powder it absorbs the UV and then emits it as blue colour (which we associate with clean clothing, which is why the washing powder people add it to the mix).
Meanwhile phosphorescent materials, like glow-in-the-dark stars, do their emitting much more slowly. This enables them to shine for a few minutes after the bedroom lights are switched off.