A incandescent source is when an object is heated so much that it gives off light. The word incandescent means giving off light as a result of being heated. Therefore, an incandescent source means a light source that gives off light when a material is heated enough that it glows white. A very common example of an incandescent light source is the light bulbs and candles we have in our homes. In a incandescent light bulb, the electricity goes from the wires into the bulb. The electricity then gets forced to go through a very tiny and thin wire called the filament. The electrons have a tiny amount of space to go through, so the filament heats up. The filament then gets heated up that it finally glows. Incandescent light bulbs are not very efficient, however, because a large portion of the electricity is converted to heat instead of useful light.


      

The sun, a incandescent light bulb, and a candle are all incandescent sources of light.

     In a fluorescent source, a lead-in wire attached to a power source sends out a electric charge. The charge causes the mercury vapour inside the tube to give off invisible ultraviolet rays. The invisible ultraviolet rays produced inside the tube is then absorbed by the phosphor coating on the outside of the tube. When the phosphor coating on the outside absorbs the invisible ultraviolet light, it glows and gives off visible light that humans can see. Fluorescent tubes are more efficient than incandescent light bulbs because they produce less heat than incandescent light bulbs do. However, fluorescent tubes have contents that are poisonous and the tubes are also harder to dispose.



Today, fluorescent light bulbs come in different sizes and designs.

     Phosphorescent sources are similar to fluorescent sources, except phosphorescent sources store the light energy and releases them off later as visible light. Fluorescent sources release light immediately. Phosphorescent sources can store the energy and later release them off as visible light. Some glow in the dark objects like watches and toys are phosphorescent sources.


Glow in the dark items such as these contains phosphors, which store the light energy and releases them later off as light.

     When light is produced and emitted after a chemical reaction, we call this light source a chemiluminescent source. Energetic particles created by the chemical reaction gives off visible light that we can see. This is how chemiluminescent sources work. A good example of a chemiluminescent source is a glow stick. In a glow stick, there are two substances separated by a thin barrier. When this barrier is broken, the two substances mix and a chemical reaction takes place. The particles in the substances turn energetic, and in turn they produce visible light.


Glow sticks have two different chemicals, and when these two chemicals are mixed, light is produced.

     Bioluminescent sources produce light by chemical reactions inside animals. Bioluminescent sources are just like chemiluminescent sources, the only difference is that bioluminescent sources are in animals, while chemiluminescent is not. In very deep places under the ocean, there are many different kinds of fish that use bioluminescent for many purposes. In some fishes, they have a special light organ called photophores that are bioluminescent sources. These light organs produce light to attract the fish's prey.



      

The Japetella, Aequorea Victoria, and Carinaria are all deep sea creatures that create their own light by bioluminescent.