photon flux

photon flux

[′fō‚tän ‚fləks]
(optics)
The number of photons in a light beam reaching a surface, such as the surface of the photocathode of a photomultiplier tube, in a unit of time.
McGraw-Hill Dictionary of Scientific & Technical Terms, 6E, Copyright © 2003 by The McGraw-Hill Companies, Inc.
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PPFD Blue light Shade net (400-700nm) (400-500nm) Black 615.2 [+ or -] 4.6d * 141.8 [+ or -] 1.7f Aluminized 690.0 [+ or -] 1.8c 169.2 [+ or -] 1.3b Grey 707.5 [+ or -] 5.5b 162.3 [+ or -] 1.6c Perl 695.4 [+ or -] 3.6c 150.4 [+ or -] 1.4e Blue 759.7 [+ or -] 4.2a 192.9 [+ or -] 1.4a Red 761.2 [+ or -] 5.9a 158.8 [+ or -] 1.6d Red light Shade net (600-700nm) Black 255.4 [+ or -] 2.0e Aluminized 274.9 [+ or -] 2.3d Grey 293.7 [+ or -] 2.1c Perl 298.8 [+ or -] 2.7b Blue 295.2 [+ or -] 2.0bc Red 358.4 [+ or -] 2.6a PPFD = photosynthetic photon flux density.
Instead of the familiar foot-candles or lux (illuminance--the quantity of light falling on a given area), you'd probably be presented with a target value for photosynthetic photon flux density (PPFD), which is the number of photosynthetically active photons that impinge on the surface of the plants each second.
The unit of measurement is called the photosynthetic photon flux density (PPFD) and is defined as micromoles per square meter per second ([micro]mol/[m.sup.2]/s).
The photonic efficiency (Z) of the NO degradation is calculated from the degradation rate of NO and the incident photon flux according to the following equation [33]:
Chou and Wen note, however, that while many soft X-ray sources and their characteristic photon flux densities are generally assumed to cause negligible changes to the adsorbate in PSD studies, particular systems can exhibit variation in chemical-bonding structure, especially when high-intensity SR is used [23].
Measurements of net photosynthesis (A), transpiration rate (E), stomatal conductance (gs), photosynthetic photon flux density (PPFD), leaf temperature (LT), water use efficiency (WUE) and vapor pressure deficit (VPD) were performed using an infrared gas analysis system (IRGA--ADC-LCA-4, Hoddesdon, UK).
3.2 Cross section of an hydrogen ion from photon flux
Conventionally, these nonlinear processes are assumed to occur only at the focal volume where extremely high photon flux is generated, allowing for noninvasive three-dimensional optical sectioning.
These differences are consistent with the results found in this work, where there is a reduction in photon flux up to 98% with the inclusion of the flattening filter and low-energy photon beam filtering is effective.
Where w = 2[pi]f , k(r) is a diffusion coefficient, [phi](r) is a photon flux density at the position r, c is the speed of light in a medium and [[mu].sub.a] (r) is the absorption coefficient.