Light has to come from somewhere, right? It doesn’t just pop into existence. There are several ways in which light is produced. Substances that produce light are called luminous. Substances that do not produce are called non-luminous. Here are some ways in which light in produced:
Incandescence: When metal is placed in a heat source, such as an oven, after a while, it will start to glow, from red, to orange, to yellow, to white, and finally to blue. These colours represent a source of heat and light. When light is produced this way, it is called incandescence. Incandescent light bulbs are an example:
Electric Discharge: Light can be created when electricity is released, called an electric discharge. The example that comes first to mind is lightning. However, other forms of electric discharge are used, for example neon lights. An electric current is passed through a gas to produce a glow. Different gases produce different colours; neon is red, argon is violet.
Phosphorescence: You’ve probably heard of “glow-in-the-dark”, whether it be a bracelet or a toy or a decoration. These are all examples of phosphorescence. Materials are coated with phosphors, a special substance that absorbs ultraviolet light. When they are in the dark, where there are no UV rays to absorb, they give off light. They do not release this light immediately, but rather, hold on to it for a certin period of time.
Fluorescence: Fluorescent light is much like phosphorescent light, with the difference being that they release their absorbed ultraviolet light right away. Products that claim to whiten or brighten objects use this science, such as highlighters and laundry detergents.
Chemiluminescence: This type of light is also called “cold light” because it is a by-product of a chemical reaction that produces no heat, only light.
Bioluminescence: Bioluminescence is quite simply chemiluminescence occuring in living organisms (such as fireflies, and certain types of fish).
Triboluminescence: A rare form of light that occurs when certain types of crystals are rubbed together, crushed, or scratched.
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