Incandescence

Incandescence is the release of visible light from a hot body due to its high temperature (black body radiation). It is therefore visible thermal radiation (compare this to the invisible infrared radiation from the human body).

The filament of an incandescent light bulb heats up due to resistance to the electrical current. This heated filament releases visible light in the form of black body radiation. Pure white light (daylight) is released at about 6,500 kelvin (yellow light comes from a cooler filament). This is why the color temperature of a computer monitor is often set to 6,500 K (D65).

[edit] Fluorescence vs. Incandescence

Compare incandescence to fluorescence (visible luminescence) caused by excited electrons releasing photons as they drop down from a higher atomic orbital to lower one. This is the mechanism of a fluorescent lamp and a light-emitting diode. The energy of the fluorescent lamp comes from absorption of kinetic energy carried from electrons emitted by the cathode, whereas the energy a light-emitting diode comes from the energy of the electrons passing through the semiconductor.

Radiation Process	Process for Visible Light	Domestic Appliance	Energy Source
thermal radiation	incandescence	incandescent light bulb	black body radiation from a hot filament
luminescence	fluorescence	fluorescent lamp	kinetic energy from electrons emitted by the cathode striking gas molecules which then release photons
luminescence	fluorescence	light-emitting diode (LED)	energy from electrons moving through the semiconductor