Activity Title: Ultraviolet detection beads


Why do the beads change colour?

UV beads contain a chemical that is photochromic. This means that the chemical changes colour when exposed to ultraviolet radiation. Normally the beads are colourless but when UV light strikes them the structure changes. This allows the beads to absorb visible light and the colour changes. When taken out of UV light the molecules go back to the original state and lose the colour. This can happen over and over but it is best to keep the beads out of UV light as much as possible.

Video 1: Orange beads


The orange beads have a very clear change.

Video 2: Purple beads


The purple beads change colour very quickly when exposed to sunlight. See if you can stop the video before the colour change is complete.

Video 3: Yellow beads


The yellow beads seem to change colour very slowly.

Video 4: All colours


In this example there is a random selection of colours.