phosphores

Phosphors are substances that exhibit phosphorescence, a type of luminescence. Luminescence is the emission of light by a substance not resulting from heat. Phosphorescence is specifically characterized by a delayed emission of light after the initial excitation source has been removed. This means that a phosphorescent material will continue to glow for some time after being exposed to light or other forms of energy.

The process of phosphorescence involves the absorption of energy, typically from ultraviolet or visible light. This energy excites electrons within the phosphor material to higher energy levels. However, instead of immediately returning to their ground state and releasing the energy as light, some electrons become trapped in metastable energy states. When these electrons eventually transition back to their ground state, they release the stored energy as photons of light, causing the material to glow. The duration of this glow depends on the specific phosphor material and the nature of the traps.

Phosphors are widely used in various applications. A common example is in glow-in-the-dark toys and paints, where they absorb ambient light during the day and then emit a soft glow in the dark. They are also utilized in fluorescent lamps, where they convert ultraviolet radiation into visible light. In some display technologies, such as older cathode ray tube (CRT) televisions and oscilloscopes, phosphors were used to create the images on the screen by being excited by an electron beam. The color of the emitted light is determined by the chemical composition of the phosphor.