Incandescence is the emission of electromagnetic radiation (including
visible light) from a hot body as a result of its temperature. The
term derives from the Latin verb incandescere, to glow white.
Incandescence is a special case of thermal radiation. Incandescence
usually refers specifically to visible light, while thermal radiation
refers also to infrared or any other electromagnetic radiation.
For information on the intensity and spectrum (color) of
incandescence, see thermal radiation.
1 Observation and use
2 Figurative use
3 See also
5 External links
Observation and use
Main article: Thermal radiation
In practice, virtually all solid or liquid substances start to glow
around 798 K (525 °C) (977 ˚F), with a mildly dull red
color, whether or not a chemical reaction takes place that produces
light as a result of an exothermic process. This limit is called the
Draper point. The incandescence does not vanish below that
temperature, but it is too weak in the visible spectrum to be
At higher temperatures, the substance becomes brighter and its color
changes from red towards white and finally blue.
Incandescence is exploited in incandescent light bulbs, in which a
filament is heated to a temperature at which a fraction of the
radiation falls in the visible spectrum. The majority of the radiation
however, is emitted in the infrared part of the spectrum, rendering
incandescent lights relatively inefficient as a light source. If
the filament could be made hotter, efficiency would increase; however,
there are currently no materials able to withstand such temperatures
which would be appropriate for use in lamps.
More efficient light sources, such as fluorescent lamps and LEDs, do
not function by incandescence.
Sunlight is the incandescence of the "white hot" surface of the sun.
The word incandescent is also used figuratively to describe a person
who is so angry that they are imagined to glow or burn red hot or
The visible color of an object heated to incandescence (from 550°C to
List of light sources
Dionysius Lardner (1833). Treatise on Heat. Longman, Rees, Orme,
Brown, Green & Longman. Archived from the original on 2017-12-21.
The state in which a heated body, naturally incapable of emitting
light, becomes luminous, is called a state of incandescence.
^ John E. Bowman (1856). An Introduction to Practical Chemistry,
Including Analysis (Second American ed.). Philadelphia: Blanchard and
Lea. Archived from the original on 2017-12-21.
^ William Elgin Wickenden (1910). Illumination and Photometry.
McGraw-Hill. Archived from the original on 2017-12-21.
^ Koones, Sheri (2012-10-01). Prefabulous + Almost Off the Grid: Your
Path to Building an Energy-Independent Home. Abrams.
^ Example 1:'...the stadium positively crackled with the incandescent
anger of anguished supporters.' Mark Wilson, 'Rangers 1 Unirea 4',
Daily Mail, 21 October 2009 "Archived copy". Archived from the
original on 2009-10-23. Retrieved 2009-11-01. . Example 2:
'...there's something very funny about incandescent anger.' Mark
Fisher, 'Jerry has a cross to bear', The Scotsman, 5 March 2006 .
Figurative use: Rangers 1 Unirea-Urziceni 4 etc.
Methods of generation
Parabolic aluminized reflector (PAR)
Fluorescent lamp (compact)
Hydrargyrum medium-arc iodide (HMI)
Hydrargyrum quartz iodide (HQI)
Stage lighting instrument
Intelligent street lighting