color temperature(redirected from light appearance)
color temperatureSymbol: T c. The surface temperature of a star expressed as the temperature of a black body (i.e. a perfect radiator) whose energy distribution over a range of wavelengths corresponds to that of the star. It can thus be found by matching the energy distribution in the star's continuous spectrum to that of a black body (given by Planck's radiation law). With increasing temperature the star emits a higher proportion of blue and ultraviolet radiation and the position (wavelength) of maximum radiated energy on the energy distribution curve shifts accordingly; the basic shape of the curve remains unchanged (see illustration). Color temperature is related to color index (B –V) by an approximation of Planck's radiation law:
As a star's spectrum is not precisely that of a black body, the color temperature and effective temperature are not equal: the difference is greatest for hot (O and B) stars. Although the color temperature is not as closely related to the star's surface temperature as is the effective temperature, it has the advantage of being found by measurements of the star's color index. The Sun's color temperature is 5700 K.
(Tc), a parameter that characterizes the variation of the intensity I(λ) of the radiation from some source with wavelength λ in the optical region of the continuous spectrum. The color temperature of a source is equal to the temperature of a blackbody that has the same relative distribution of intensity as the source in the wavelength range in question (seePLANCK’S RADIATION LAW). The color temperature characterizes the relative contribution of radiation of a given color to the radiation of the source; that is, it characterizes the apparent color of the source. The concept of color temperature is widely used in astrophysics, mainly in the study of the spectral energy distribution of stars (seeTEMPERATURE).
color temperature[¦kəl·ər ¦tem·prə·chər]
color temperatureThe color of light, expressed in Kelvins (K). The sun is about 5800 Kelvins. This is called a "temperature," because the hotter fire gets, the more it changes from a warm yellow glow to white.
The lower the Kelvin rating, such as the common incandescent/tungsten bulb, the warmer, softer and more yellow the light. The higher the K number, the cooler, whiter and bluer the light. See white balance.
Approximate TemperatureLight In Degrees ofSource Kelvin (K) Match/Candle 1,700-1,800 Warm/More Incandescent 2,600-3,000 Yellow| Halogen 2,800-3,400 || Fluorescent 3,000-4,300 Daylight| Outdoor sun 5,000-6,000 || Outdoor shade 6,000-7,000 Cool/Whiter/ North sky 10,000+ Bluer LED lights range approximately from 2,600 to 5,200 K
|From Warm to Cool|
|Increasingly, light bulb packages show the color temperature as a measure from warm to cool. This is a halogen bulb label.|