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Phosphorescence |
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What is phosphorescence?
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Phosphorescence is just another way light is given off from a materials. The main difference is that the amount of time that the electron stays in the excited state is much longer than with other forms of luminescence. This means that the light is �time released,� or in other words the light continues even after the energy source has ceased.
Phosphorescence was first noticed in the 17th century, but it wasn�t until the 19th century that research began. A German physicist by the name of Philipp Lenard spent forty years of his life studying phosphorescence. Lenard theorized that when energy is absorbed by a phosphorescent material, some of the elections are displaced. The electrons are trapped in potential troughs, and are not released until temperature related energy fluctuations. The release of the electron is when the light is produced. |
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Metaphorical Description: |
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Representing the situation metaphorically with the rock, it as if the rock is placed on a table. The rock doesn�t fall back to the ground until time has passed. With luminescence the electron remains in the excited state for about 1/1000 of a second. However, with phosphorescence the electron might stay in the excited state for as long as a few hours. |
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Uses: |
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Phosphorescent products are very popular today. There are some very practical uses, and of course sometimes phosphorescence is simply used for fun. One place that you often find a phosphorescent substance is on watches (see picture). By simply exposing the watch to a light for a few seconds, you are able to read it in the dark for hours to come. Also, this same type of material is used in many bedrooms. Lots of people imitate the stars by using phosphorescent stickers. When you turn out the lights to rest, it is like sleeping under the stars. |
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Importance of Phosphorescence: |
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Possibly the most important use of phosphorescent materials is in safety. In large buildings it is very important to know how to exit the building in the case of an emergency. The traditional �EXIT� signs have always been lit with electricity in the past, but what happens if the power source is cut off? How do you find your way outside? This is where phosphorescent materials come into play. If you use a material that glows in the dark, then there will always be a lighted sign in the case of an emergency. |
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