Incandescence

Hot metalwork

Incandescence

Example incandescence colors (temperature range 550 - 1300 C)

Incandescence is the emission of electromagnetic radiation, including visible light, from a hot body as a result of its temperature. This phenomenon is a form of black-body radiation and is distinct from other forms of light emission such as fluorescence, phosphorescence, and bioluminescence.

Overview

Incandescence occurs when a material becomes hot enough to emit light visible to the human eye. The process is a result of the thermal agitation of atoms and molecules within the material. As these particles are heated, they gain energy and move more rapidly. Electrons within the atoms can be excited to higher energy levels and, upon returning to their original levels, release photons. The color of the light emitted depends on the temperature of the material, following Planck's law of black-body radiation. Materials at lower temperatures emit light in the red part of the spectrum, while hotter materials emit light in the blue.

Physical Principles

The basis of incandescence is the black-body radiation that any body emits if it is not in a state of absolute zero. According to Planck's law, the spectrum of black-body radiation is determined solely by the body's temperature. This principle allows for the determination of a body's temperature by observing the color of its incandescence, a method commonly used in pyrometry.

Applications

Incandescence is utilized in various applications, most notably in incandescent light bulbs, where an electric current heats a filament, typically made of tungsten, until it glows. Other applications include heating elements in electric heaters, the production of light in halogen lamps, and as a method for observing the temperature of materials in scientific research.

Environmental and Economic Considerations

The efficiency of incandescent lighting is significantly lower than that of newer technologies such as LED lighting and compact fluorescent lamps (CFLs). A large portion of the energy consumed by an incandescent bulb is emitted as infrared radiation, which is invisible to the human eye and thus does not contribute to the lighting purpose. This inefficiency has led to the phasing out of incandescent bulbs in many countries in favor of more energy-efficient alternatives.

See Also

• Black-body radiation
• Electromagnetic spectrum
• Light emission
• Temperature measurement