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An action spectrum is a graph of the rate of biological effectiveness plotted against wavelength of light. [1] It is related to absorption spectrum in many systems. Mathematically, it describes the inverse quantity of light required to evoke a constant response.
A key finding of modern photochemical action plots [32] is that the absorption spectrum of a photoreactive molecule or reaction mixture correlates poorly with photochemical reactivity as a function of wavelength in many cases. Initial studies showed a significant red-shift in photopolymerization yield compared to the absorption spectrum of the ...
Solar spectrum with Fraunhofer lines as it appears visually. A material's absorption spectrum is the fraction of incident radiation absorbed by the material over a range of frequencies of electromagnetic radiation. The absorption spectrum is primarily determined [2] [3] [4] by the atomic and molecular composition of the material.
Narrow-spectrum antibiotics have low propensity to induce bacterial resistance and are less likely to disrupt the microbiome (normal microflora). [3] On the other hand, indiscriminate use of broad-spectrum antibiotics may not only induce the development of bacterial resistance and promote the emergency of multidrug-resistant organisms, but also cause off-target effects due to dysbiosis.
PAR as described with PPF does not distinguish between different wavelengths between 400 and 700 nm, and assumes that wavelengths outside this range have zero photosynthetic action. If the exact spectrum of the light is known, the photosynthetic photon flux density (PPFD) values in μmol⋅s −1 ⋅m −2) can be modified by applying different ...
The action spectra of chlorophyll molecules are slightly modified in vivo depending on specific pigment–protein interactions. The process of photosynthesis provides the main input of free energy into the biosphere, and is one of four main ways in which radiation is important for plant life.
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The UV power spectrum (expressed as watts per square meter per nanometer of wavelength) is therefore multiplied by a weighting curve known as the CIE-standard McKinlay–Diffey erythemal action spectrum. [9] [10] There are some older formulas for the spectrum, resulting in differences of up to 2%. [11] The result is integrated over the whole ...