Re: 450nm-es fényforrás?

[HWSW Famulus]

> Candella: alap SI mértékegység, de az istennek se találtam definiciót. A 
> fényerősség mértékegysége, ennek lehet direkt kapcsolata a W-tal. De mi?
>
> hjozsi

candela (cd)
the SI base unit for measuring the intensity of light. Candela is the Latin 
word for "candle." The unit has a long and complicated history. Originally, 
it represented the intensity of an actual candle, assumed to be burning 
whale tallow at a specified rate in grains per hour. Later this definition 
was replaced with a definition in terms of the light produced by the 
filament of an incandescent light bulb. Still later a standard was adopted 
that defined the candela as the intensity of 1/600 000 square meter of a 
"black body" (a perfect radiator of energy) at the temperature of freezing 
platinum (2042 K) and a pressure of 1 atmosphere. This definition has also 
been discarded, and the candela is now defined to be the luminous intensity 
of a light source producing single-frequency light at a frequency of 540 
terahertz (THz) with a power of 1/683 watt per steradian, or 18.3988 
milliwatts over a complete sphere centered at the light source. The 
frequency of 540 THz corresponds to a wave length of approximately 555.17 
nanometers (nm); normal human eyes are more sensitive to the yellow-green 
light of this wavelength than to any other. In order to produce 1 candela of 
single-frequency light of wavelength l, a lamp would have to radiate 
1/(683V(l)) watts per steradian, where V(l) is the relative sensitivity of 
the eye at wavelength l. Values of V(l), defined by the International 
Commission on Illumination (CIE), are available online from the Color and 
Vision Research Laboratories of the University of California at San Diego 
and the University of Tübingen, Germany.