The molecular absorption bands of water and carbon dioxide cause “deep” absorption features that, in two bands near 1.4 μm and 1.9 μm, completely block transmission of radiation. /Subtype /Image 0000035672 00000 n
For a low-iron glass, the near-normal total solar transmittance is approximately 90%. FIGURE 2-4. 0000003809 00000 n
Although it’s not so much geared towards saving energy as other ratings, visible transmittance is one of the important properties that goes into rating windows. for n2 = 1.38 and from eqn [25], ρ = 2.8%, leading to a single sheet reflectance of 5.2%, instead of 8% for uncoated glass. This application is the motivation for the MODIS band 26 (Table 1-1). Optical glass; lower usable limit about 310 nm. The irradiance at the surface depends on the incident angle, being a maximum if the surface is perpendicular to the incident angle, and less as the angle decreases. However, there are other factors such as the frame, sash and grids. 0000031188 00000 n
Window area and configuration can significantly affect the overall window assembly U-Factor. endobj Average value of transmittances in steps of 10 nm from 400 to 700 nm. For microwave measurements, radiances can be almost independent of temperature. Visible transmittance can also help you save money. Second, the distance at which S is maximum increases as bNo increases (brighter landscapes). We measured all the graphs at i=0°. 0000008660 00000 n
We now must modify Eq. These curves differ from the one in Fig. (a) corresponds to a shadowed vista with a scattering angle of 15° and bNo = 0.13Ns, and (b) corresponds to an illuminated vista with a scattering angle of 125° and bNo = 0.5Ns. The intensity of the solar radiation on the Earth’s surface is also presented for comparison. The infinite thickness is specified to ensure that reflected flux from no other interface can contribute to that reflected by the interface of interest, and to ensure the collection of subsurface flux scattered by molecules of the material. solar energy transmittance. 2-4 and Fig. Optical glasses are optimized to provide excellent transmittance throughout the total visible range from 400 to 800 nm. This is largely the result of light being scattered out of the solar path by air molecules, whose diameter is less than λ/π (Slater, 1980). Although symbols have been standardized for most of these properties, there are a few exceptions. The reflection from all three interfaces produces destructive interference and antireflection. The energy balance of a glass unit is determined on one side by its heat losses, and on the other one by its solar heat gains. Fig. The index of refractionrefers to the ratio of the speed of light in a vacuum to the speed of light through a given material at a given wavelength, while the Abbe nu… Usually the transmittance range spreads also into the near UV and IR regions. Transmission of visible light determines the effectiveness of a type The AccuPAR LP-80 (Decagon Devices Inc., Pullman, WA, USA; see Figure 4) is a model of line quantum sensor making use of 80 individual sensors on a probe and a control unit. Large particles and particles that absorb light contribute to path radiance differently than do fine particles that only scatter light. The curves are the results of typical transmission measurements of more or less current production batches and only give an overview of the approximate or typical transmission behavior. 0000005454 00000 n
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Since cirrus clouds are above most of the atmosphere's water vapor, they return a signal to a high-altitude sensor, while the signals from the earth's surface and lower altitude clouds are absorbed in the 1.4 μm band. 2-5. UV Transmittance- The percentage of energy in the ultraviolet (UV) spectrum, from 300 to 380 nanometers, that is directly transmitted through the glass. Designs that increase the wavelength range do so at the expense of input angle range, and vice versa. electro-magnetic spectrum. 0000016322 00000 n
For particle sizes in the range from about λ/π to about 2λ/π, there is a wavelength dependence that is less than that of Rayleigh scattering. For example, you might find a window with very high visible transmittance but that may be at the expense of a higher solar heat gain coefficient. The diagram shows a dip of transmittance at $\approx 1200\,$ nm. ScienceDirect ® is a registered trademark of Elsevier B.V. ScienceDirect ® is a registered trademark of Elsevier B.V. URL: https://www.sciencedirect.com/science/article/pii/B9781785481604500042, URL: https://www.sciencedirect.com/science/article/pii/B9780128044506000036, URL: https://www.sciencedirect.com/science/article/pii/B978012369407250005X, URL: https://www.sciencedirect.com/science/article/pii/B9780080878720003103, URL: https://www.sciencedirect.com/science/article/pii/B9780123822253003558, URL: https://www.sciencedirect.com/science/article/pii/B0122274105005901, URL: https://www.sciencedirect.com/science/article/pii/B9780080878720003048, URL: https://www.sciencedirect.com/science/article/pii/B0122274105006487, URL: https://www.sciencedirect.com/science/article/pii/B978012409548909076X, Land Surface Remote Sensing in Urban and Coastal Areas, How the Transfer of Light (Radiation) through the Atmosphere Affects Visibility, (Images and description courtesy NASA/GSFC/JPL, MISR Science Team.