Phosphorescence is the luminescence that occurs in certain materials due to the absorption of electromagnetic radiation. When electromagnetic radiation such as a ray of ultraviolet light falls on the surface of the phosphorescent object, the atoms of the object tend to absorb the energy, get excited, and jump to the excited state. The excited state of atoms is highly unstable in nature, which is why the excited atoms soon begin to lose energy and move from high energy excited state to low energy ground state. The return of an atom towards the ground state leads to the emission of photons and radiation of light energy into the environment. As compared to the fluorescent materials, the phosphorescent materials tend to emit light radiations into the environment at a relatively slower rate. Impure barite was the first known phosphorescent material that was discovered by Italian alchemist Vincenzo Casciarolo in the year 1602. At that time, it was known as the stone that absorbs the sunlight and emits light in the darkness during the night like the moon. Later other minerals were also identified that exhibited the same phenomena. The phenomenon of phosphorescence is a type of photoluminescence as it makes use of the absorption of photons to produce light. The maximum glow of phosphorescent objects can be observed when placed in dark areas.
Examples of Phosphorescent Light
A number of objects used in our daily life make use of the phosphorescence phenomenon to emit light energy into the environment. A few examples of phosphorescent light in real life are given below:
1. Glow in Dark Toys
The glow in the dark toys tends to form one of the most prominent examples of objects that emit light radiations into the surroundings with the help of the phosphorescence phenomenon. Such toys are generally coated with a layer of phosphorescent material that tends to radiate light energy in the surroundings upon absorption of electromagnetic radiations.
Some of the stickers used for decoration purposes are capable of exhibiting a phosphorescence effect in real life. This is usually done by applying a thin layer of phosphorescent material to the surface of the stickers. The sticker surface releases the stored energy at a slow rate, thereby providing a glowing effect.
The dials of some of the watches glow when they are placed in dark places. This is mainly due to the phosphorescence of the element present in the structure of the watches and clocks. This helps improve visibility during the nighttime or in dark places.
Some of the paints tend to provide a glowing effect due to the phosphorescent element present in them. Such paints are generally preferred for decoration purposes during festivals such as Halloween.
5. Safety Signs
Safety signs are generally provided with a phosphorescent coating to improve the visibility of the caution during the nighttime. This helps prevent accidents and can be used to enhance the appearance of the signboards.
Various minerals such as celestite, colemanite, sphalerite, calcite, willemite, and fluorite, etc. tend to emit light radiations into the environment due to the phosphorescence phenomenon. Most of these minerals exist naturally; however, some of them can be created artificially. Various types of diamond are also known to exhibit phosphorescence in the environment. Other elements such as white topaz, chlorophane, etc. are also some of the prime minerals that display the phenomenon of phosphorescence in real life.