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Basic Thermal Physics: Heat Exchange and Infrared Radiation
Published in Kurt Ammer, Francis Ring, The Thermal Human Body, 2019
Radiant flux, dφ/dA, is the radiant flow per unit area (unit:W m−2). The radiant flux emitted by a surface is the thermal radiant exitance. The radiant flux incident on or passing through an area is the irradiance.
ENTRIES A–Z
Published in Philip Winn, Dictionary of Biological Psychology, 2003
The radiant flux of a source is the total amount of energy emitted as electromagnetic radiation, integrated across all wavelengths. RADIOMETRY is the assessment of this quantity. In practical terms, radiometric measurements pose many challenges due to the fact that no single detector device has a uniform response to all wavelengths. PHOTOMETRY (from Greek, photos: light) is a special case of radiometry and is concerned with measuring the radiant energy that stimulates the human eye, and is conducted with a photo-detector that has the same SPECTRAL SENSITIVITY as a hypothetical 'standard observer'. This spectral sensitivity is defined by the LUMINOUS EFFICIENCY FUNCTION, a curve of LUMINOSITY COEFFICIENTS (the proportion of incident light energy absorbed at the retina) for the range of visible wavelengths. These coefficients are derived from measurements of the intensity of the sensation of BRIGHTNESS or LUMINOSITY at different wavelengths, induced by a source of constant energy (the LUMINOSITY CURVE). Luminous efficiency functions have been defined for the light adapted eye (the photopic curve) and the dark adapted EYE (the scotopic curve) (see SCOTOPIC vs. PHOTOPIC) corresponding to the visual response mediated by the photoreceptor systems of CONES and RODS respectively.
Energy Medicine
Published in Len Wisneski, The Scientific Basis of Integrative Health, 2017
Irradiance is the amount of light illuminating a surface. Another way of defining irradiance is by the average amount of energy per unit area, per unit time—a description of a type of surface brilliance. In the past, physicists generally used the term intensity to mean the flow of energy per unit area, per unit time; the term has been slowly replaced by irradiance. The irradiance density, energy density, or irradiance dose is measured in joules per treated square centimeter (J/cm2). The time rate of the flow of radiant energy is referred to as the optical power or radiant flux, which is measured in watts. One way of conceptualizing the power of a laser beam is by the rate at which the beam delivers the optical energy; thus, a laser with high power is delivering the optical energy faster than a laser with low power. Power is the ratio of energy and time. Energy, which is measured in joules, is the amount of light delivered to the tissue over the treatment time. The energy of a laser beam (joules) is equal to the beam's average power (watts), multiplied by the number of seconds the beam is delivering energy (treatment time). Therefore, a laser with more average power (watts) can deliver the same amount of energy (joules) in less time. Radiant flux density is obtained by dividing the radiant flux (i.e., power) by the area of the treated tissue. Radiant flux density (power density) and the irradiance dose (energy density) are the most important parameters in determining the clinical effectiveness of a laser (Hode and Tunér, 2014; Kreisel and Weber, 2012). In reviews of the research literature of studies that produced negative results with laser therapy, too low a dose was the single most significant factor in treatment failure (Hode and Tunér, 2014; Schindl et al., 2000).
Entraining effects of variations in light spectral composition on the rest-activity rhythm of a nocturnal rodent
Published in Chronobiology International, 2019
Melissa A. B. de Oliveira, Marina Scop, Ana Carolina Odebrecht Abreu, Paulo Roberto Stefani Sanches, Augusto Camargo Rossi, Antoni Díez-Noguera, Maria Elisa Calcagnotto, Maria Paz Hidalgo
Figure 1 illustrates the spectral composition of these two lighting systems. The irradiance of both light sources was similar (radiant flux = 10W, luminous flux = 1500 lumens). The RGB-v lighting system gave a luminous flux between 150 and 400 lux at cage level depending on the cage position inside photoperiod station, while the RGB-f gave a luminous flux (illuminance) between 200 and 450 lux at cage level. LED lamps were designed and provided by Luxion Iluminação (Caxias do Sul, Brazil; patent required n. BR 10 2015 001531–3).
The effect of capping agents on the toxicity of silver nanoparticles to Danio rerio embryos
Published in Nanotoxicology, 2019
N. Abramenko, T. B. Demidova, Yu. A. Krutyakov, P. M. Zherebin, E. Y. Krysanov, L. M. Kustov, W. Peijnenburg
Water 96 mL and 4 mL of a 30% H2O2 aqueous solution were added to 20 mL of a colloidal Ag dispersion containing 3 g/L silver and 48 g/L sodium tallow amphopolycarboxyglycinate. The mixture was treated with a UV mercury arc lamp (DRT-240) with a power of radiant flux 24.6 W. The irradiation was carried out in a spectral interval of 240–320 nm for 1 h. During this 1 h period, every 15 min the process was interrupted for 10 min under vigorous stirring.
Evaluating the blue-light hazard from solid state lighting
Published in International Journal of Occupational Safety and Ergonomics, 2019
John D. Bullough, Andrew Bierman, Mark S. Rea
As the spot size grows in this fashion, the dose (or weighted radiant energy delivered to the retina) is assumed to be constant based on the approximation used by the CIE [44,p.27] and IES [33]: D= dose; Eeff= effective weighted retinal irradiance; t= time; Φ = spectrally weighted radiant flux; k= a proportionality constant.