Why are most Glow-in-the-Dark items are green, and why do they glow?
A phenomenon named phosphorescence is responsible for the light most Glow-in-the-Dark items emit.
Phosphorescence occurs when light absorbed by an object is slowly released and can be observed even after the light is removed. If not tampered with, the light the object emits is dim, and is always pale blue in color.
Chemists had a bright idea to spark interest in this phenomenon and to make it visually stimulating. They discovered that when they mixed fluorescent dye with the phosphorescent material, the object emitted a glowing, brighter green, or sometimes red, light.
The reason for this transformation is that fluorescent compounds absorb the light and rapidly emit it, giving the compounds a glowing appearance. This phenomenon occurs only in the constant presence of the original light source.
The phosphorescent material absorbs the light, and slowly emits a pale blue light, that in turn is absorbed by fluorescent dye. The light now emitted is green or red light, depending on the type of dye used.
The most commonly used phosphorescent material used is zinc sulfide mixed with copper, and the green fluorescent dye most likely is sodium fluorescein. The most likely source or red fluorescent dye is rhodamine. Paired together, the phosphorescent material and the fluorescent material produce a ghostly, glowing green or red light, and hours of enjoyment for young and for old alike.
Source: coolquiz.com
Subject: Why are most Glow-in-the-Dark items are green, and why do they glow? 
Thu Feb 26 2009, 12:14
