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Weighting factor for photosynthesis. The photon-weighted curve is for converting PPF to YPF; the energy-weighted curve is for weighting PAR expressed in watts or joules. There are two common measures of photosynthetically active radiation: photosynthetic photon flux (PPF) and yield photon flux (YPF).
DLI is usually calculated by measuring the photosynthetic photon flux density (PPFD) in μmol·m −2 ·s −1 (number of photons in the PAR range received in a square meter per second) as it changes throughout the day, and then using that to calculate total estimated number of photons in the PAR range received over a 24-hour period for a ...
Radiative flux, also known as radiative flux density or radiation flux (or sometimes power flux density [1]), is the amount of power radiated through a given area, in the form of photons or other elementary particles, typically measured in W/m 2. [2]
In photometry, luminous flux or luminous power [citation needed] is the measure of the perceived power of light. It differs from radiant flux , the measure of the total power of electromagnetic radiation (including infrared , ultraviolet , and visible light), in that luminous flux is adjusted to reflect the varying sensitivity of the human eye ...
The relative spectral flux density is also useful if we wish to compare a source's flux density at one wavelength with the same source's flux density at another wavelength; for example, if we wish to demonstrate how the Sun's spectrum peaks in the visible part of the EM spectrum, a graph of the Sun's relative spectral flux density will suffice.
The number of photons observed per unit time is the photon flux. The photon flux per unit area is the photon irradiance if the photons are incident on a surface, or photon exitance if the emission of photons from a broad-area source is being considered. The flux per unit solid angle is the photon intensity. The flux per unit source area per ...
A flow chart describing the relationship of various physical quantities, including radiant flux and exitance. In radiometry, radiant flux or radiant power is the radiant energy emitted, reflected, transmitted, or received per unit time, and spectral flux or spectral power is the radiant flux per unit frequency or wavelength, depending on whether the spectrum is taken as a function of frequency ...
Bottom: Field line through a curved surface, showing the setup of the unit normal and surface element to calculate flux. To calculate the flux of a vector field F (red arrows) through a surface S the surface is divided into small patches dS. The flux through each patch is equal to the normal (perpendicular) component of the field, the dot ...