If you go on a camping vacation, do pack some light sticks in your kit. They are useful for getting some light without electricity or matches. And they come in lots of colours.
Uses of light sticks
Apart from camping, light sticks are used in many other places. Scuba divers use them to look at corals reefs. They are waterproof, need no electricity or fuel, and do not produce heat. After a hurricane, earthquake or fire, it's dangerous to switch on a light as there may be short circuits. It's better to use a light stick then.
They are also very popular as decorations in pubs and discos. Smaller versions of them are used to make crazy jewellery like light earrings, light bracelets, light necklaces, as dancing props, and for making Star Wars type lighted swords.
Glowsticking is a form of dance in which the dancer uses one or more coloured glowsticks. They trace out interesting patterns in the air, like the one in the picture.
So how do they work?
Light sticks are based on a simple chemical reaction. The most common reaction is hydrogen peroxide and phenol oxalate ester. The hydrogen peroxide is kept in a thin walled glass tube within the light stick, while the ester is outside it. When you tap or bend the light stick, the glass vial breaks. The peroxide is released into the ester.
First, the peroxide reacts with it to form a peroxyacid ester. This isn't very stable, so it decomposes further, releasing a lot of energy in the process. This energy is absorbed by a fluorescent dye that is coated on the inner wall of the stick. The dye then releases light. The colour of the light depends on the colour of the dye. Rhodamine B gives a red light, while rubrene gives a yellow light.
A CFL lamp also works on the principle of fluorescence, but the energy comes from electricity, not a chemical reaction.
Fireflies and glow-worms
Wondered how a firefly gives light as it flies through the evening air? A similar reaction happens in its body. An enzyme called luciferase oxidizes a chemical called luciferin. Light is released during this process. Fireflies use light to tell each other where they are. Female fireflies look like worms, so they are called glowworms. They cannot fly.
Many creatures that live deep in the sea, like squids and anglerfish also produce light. The anglerfish produces light at the tip of a long spine that grows from its head. This light attracts prey which the fish quickly gobbles up!