valonlähetintä

Valonlähde, often translated as light source, refers to any object or phenomenon that emits electromagnetic radiation in the visible spectrum. This radiation is what allows humans and other organisms to see. The most common and fundamental light source is the sun, which provides the vast majority of natural light on Earth. Other natural light sources include lightning, bioluminescent organisms like fireflies and some deep-sea creatures, and celestial bodies such as stars and the moon (though the moon primarily reflects sunlight).

Artificial light sources are numerous and have been developed through various technologies. Incandescent bulbs, a historically significant type, produce light by heating a filament until it glows. Fluorescent lamps use electricity to excite mercury vapor, producing ultraviolet light that then causes a phosphor coating inside the tube to emit visible light. Light-emitting diodes (LEDs) are a modern and increasingly dominant technology that produce light through electroluminescence in a semiconductor material. Other examples include halogen lamps, discharge lamps, and lasers, each with unique properties and applications. The study of light sources is fundamental to fields such as physics, optics, and illumination engineering, impacting everything from everyday lighting to advanced scientific instruments.