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 ?
No infants born to PHIV mothers were infected with HIV (1/32 infant lost to follow up), whereas 2% of babies born to mothers in BHIV group were found to be HIV-infected (29/595 lost to follow up).
Initiation of cART in 1st trimester more common in PHIV group can probably be attributed to the fact that the women in this group are HIV infected from birth and therefore have been given HIV health care since early childhood.
Though not significantly different, there was a trend for PHIV to be more likely to achieve viral suppression at delivery than BHIVwomen.
It may seem surprising that only 16% of PHIV women were on cART prior to pregnancy.
The prevalence of HPV was 28% in PHIV group and 19% in BHIV group.
(12,15) In this study, only one woman (3%) in PHIV group had a history of induced abortion.
A history of spontaneous abortions on the other hand tended to be more common in the PHIV group.