luminous efficacy


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Luminous efficacy

There are three ways this term can be used: (1) The luminous efficacy of a source of light is the quotient of the total luminous flux emitted divided by the total lamp power input. Light is visually evaluated radiant energy. Luminous flux is the time rate of flow of light. Luminous efficacy is expressed in lumens per watt. (2) The luminous efficacy of radiant power is the quotient of the total luminous flux emitted divided by the total radiant power emitted. This is always somewhat larger for a particular lamp than the previous measure, since not all the input power is transformed into radiant power. (3) The spectral luminous efficacy of radiant power is the quotient of the luminous flux at a given wavelength of light divided by the radiant power at that wavelength. A plot of this quotient versus wavelength displays the spectral response of the human visual system. It is, of course, zero for all wavelengths outside the range from 380 to 760 nanometers. It rises to a maximum near the center of this range. Both the value and the wavelength of this maximum depend on the degree of dark adaptation present. However, an accepted value of 683 lumens per watt maximum at 555 nanometers represents a standard observer in a light-adapted condition. See Luminous efficiency, Luminous flux, Photometry

luminous efficacy

[′lü·mə·nəs ‚ef·ə·kə·sē]
(optics)
The ratio of the total luminous flux in lumens emitted by a light source over all wavelengths to the total radiant flux in watts. Formerly known as luminous efficiency.
The ratio of the total luminous flux emitted by a light source to the power input of the source; expressed in lumens per watt.

luminous efficacy

The ratio of the total emitted luminous flux, in lumens, to the total electric power consumption in watts.
References in periodicals archive ?
1, the luminous efficacy of all the three measured luminaire types reduced when the luminaires were dimmed.
Industry-leading luminous efficacy of 91 lm/W achieved within the 25W-class
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The definition relates light to the visual cortex and the luminous efficacy function, and neither represents nonvisual responses.
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Tenders are invited for Recessed Led Pannel Square Light 36 Watt Cool White Specification Input Voltage - Ac 180-270 Volts, Total Power Consumption - 40 Watt Including Driver, Lamp Luminous Efficacy - 75-100 Luminous/W, Colur - Cool White, Cct - 6000K, Cri - 75-80, Operating Temperature 05 Centrigrade To 45 Centrigrade, Power Factor - 0.