selvudlysende

Selvudlysende is a Danish term that translates to "self-luminous" or "glowing in the dark." It refers to a phenomenon where an object or substance emits light without any external source of illumination. This emission of light can occur through various mechanisms, most notably phosphorescence and fluorescence.

Phosphorescence is a type of photoluminescence where a substance absorbs energy, typically from light, and then re-emits that energy slowly over time as visible light. This is the principle behind many glow-in-the-dark toys and paints. The material stores the light energy and releases it gradually, allowing it to glow for an extended period after the initial light source is removed. The intensity and duration of the glow depend on the specific phosphorescent material used and the amount of energy it absorbed.

Fluorescence, on the other hand, is also a form of photoluminescence but the re-emission of light occurs almost instantaneously after the excitation energy is absorbed. Once the excitation source is removed, the fluorescence stops. This effect is commonly observed in fluorescent dyes, certain minerals, and biological tissues under ultraviolet light.

In a broader context, selvudlysende might also be used metaphorically to describe something that is inherently radiant, captivating, or possesses an inner glow, though its primary scientific meaning relates to the emission of light.