Solar light, intensity

The incoming solar intensity 1/4Tt, where FT is the average total incoming solar light intensity per unit area normal to the direction of propagation outside the earth s atmosphere, 1368 W m-2, and the 1/4 factor takes into account that the solar energy is spread over the entire surface of the earth (see Fig. 14.2a). 

In many cases of practical interest, the incident light—solar radiation for example—is distributed willi respect to wavelength. The contribution to the integrated intensity / from the wavelength range A to A. + dX is... 

First, zooplankton may adapt or alter their seasonal or spatial distribution to reduce the UV-stress. Seasonal life cycle adaptations to avoid periods of peak solar intensity may very well be a strategy for UV-exposed and sensitive organisms, yet this is not explicitly demonstrated. Diurnal vertical migration is, however, commonly accredited to direct UVR [8,9]. A critical question is whether organisms have a sufficient spectral resolution to separate UVR from, for example, blue light. This may be important to respond to an increased UVR under constant PAR. Such behavioral responses clearly are important evolutionary traits for swimming animals, and could affect both productivity and trophic interactions the topic will be fully covered in another chapter, and will thus only briefly be touched upon here to illustrate some ecological implications. 

Shapiro and Robertson (59, 60) evaluated 79 dyes as solar radiation protectants for spsy moth, Lymantria dispar nucieopolyhedrovirus (Ivertical distance of 50 cm from the light bulb (intensity). Congo red was die only dye tested that fully retain LdMNPV activity after artificial solar radiation exposure. Solar protectants absorbed at 280-320 nm (UV-B), as well as 320-400 nm (UV-A) (Table 3). 

Mora-Ser6 I, Garcia-Belmonte G, Boix PP, Vazquez MA, Bisquert J (2009) Impedance characterisation of highly efficient silicon solar cell under different light illumination intensities. Energe Environ Sci 2 678-686... 

In the calculation for atmospheric photodissociation reactions, how to calculate the effective solar intensity is a major issue, because not only direct irradiation from the sun, but light from all directions reflected and scattered by the ground surface, clouds, atmospheric molecules, and aerosols can contribute to photolysis. Furthermore, in the troposphere for example, only solar radiation that has not been absorbed by atmospheric molecules in the higher atmosphere, the stratosphere and above, can cause photolytic reactions. The spherically integrated solar intensity after considering those many atmospheric processes is called the actinic flux F (X) (photons cm s ), which means solar irradiation valid for photochemical effect. In atmospheric chemistry, jp is often used instead of kp for representing photolysis rate constant. Photodissociation rate constant in the atmosphere can be expressed using these parameters as... 

Fig. 1. The energy levels in a semiconductor. Shown are the valence and conduction bands and the forbidden gap in between where represents an occupied level, ie, electrons are present O, an unoccupied level and -3- an energy level arising from a chemical defect D and occurring within the forbidden gap. The electrons in each band are somewhat independent, (a) A cold semiconductor in pitch darkness where the valence band levels are filled and conduction band levels are empty, (b) The same semiconductor exposed to intense light or some other form of excitation showing the quasi-Fermi level for each band. The energy levels are occupied up to the available voltage for that band. There is a population inversion between conduction and valence bands which can lead to optical gain and possible lasing. Conversely, the chemical potential difference between the quasi-Fermi levels can be connected as the output voltage of a solar cell. Fquilihrium is reestabUshed by stepwise recombination at the defect levels D within the forbidden gap.

The dependence of 7 on 2 results in a layer of O3, the upper portion of the layer being controlled by the exponential decrease of Pq with altitude. The lower part of the layer is controlled by the fall-off of intensity of UV light as the solar beam penetrates into the increasingly dense atmosphere. More extensive treatments of this phenomenon can be found, e.g. in Wayne (1985, p. 117 ff.). 

Here B is the world average burden of anthropogenic sulfate aerosol in a column of air, in grams per square meter. The optical depth is then used in the Beer Law (which describes the transmission of light through the entire vertical column of the atmosphere). The law yields I/Iq = where I is the intensity of transmitted radiation, Iq is the incident intensity outside the atmosphere and e is the base of natural logarithms. In the simplest case, where the optical depth is much less than 1, (5 is the fraction of light lost from the solar beam because of... 

Room-temperature fluorescence (RTF) has been used to determine the emission characteristics of a wide variety of materials relative to the wavelengths of several Fraunhofer lines. Fraunhofer lines are bands of reduced intensity in the solar spectrum caused by the selective absorption of light by gaseous elements in the solar atmosphere. RTF studies have recently included the search for the causes of the luminescence of materials and a compilation of information that will lead to "luminescence signatures" for these materials. For this purpose, excitation-emission matrix (EEM) data are now being collected. 

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