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The luminous efficacy of the source is a measure of the efficiency of the device with the output adjusted to account for the spectral response curve (the luminosity function). When expressed in dimensionless form (for example, as a fraction of the maximum possible luminous efficacy), this value may be called luminous efficiency of a source ...
The standard luminous efficiency function is normalized to a peak value of unity at 555 nm (see luminous coefficient). The value of the constant in front of the integral is usually rounded off to 683 lm/W. The small excess fractional value comes from the slight mismatch between the definition of the lumen and the peak of the luminosity function.
Luminous efficacy is measured in lumens per watt (lm/W). The luminous efficiency of a source is defined as the ratio of its luminous efficacy to the maximum possible luminous efficacy, which is 683 lm/W. [80] [81] An ideal white light source could produce about 250 lumens per watt, corresponding to a luminous efficiency of 37%. [82]
The luminous efficacy of a typical CFL is 50–70 lumens per watt (lm/W) and that of a typical incandescent lamp is 10–17 lm/W. [38] Compared to a theoretical 100%-efficient lamp (680 lm/W), CFL lamps have lighting efficiency ranges of 7–10%, [39] versus 1.5–2.5% [40] for incandescents. [41]
A filament may also break, disabling the lamp. This tube failed after it had been turned on many times. Too much of the thermionic emission mix had sputtered off the cathodes, sticking to and blackening the glass. The filament of a low-pressure mercury gas-discharge lamp, with white thermionic emission coating acting as hot cathode.
Luminous efficiency, luminous coefficient V: 1: ... or the brightness of an incandescent filament of specific design. One of the best-known of these standards was the ...
This allows the filament to operate at a higher temperature than a standard incandescent lamp of similar power and operating life; this also produces light with higher luminous efficacy and color temperature. The small size of halogen lamps permits their use in compact optical systems for projectors and illumination. The small glass envelope ...
A 230-volt LED filament lamp, with an E27 base. The filaments are visible as the eight yellow vertical lines. An assortment of LED lamps commercially available in 2010: floodlight fixtures (left), reading light (center), household lamps (center right and bottom), and low-power accent light (right) applications An 80W Chips on board (COB) LED module from an industrial light luminaire, thermally ...
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