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The selectivity is defined as the ratio of solar radiation absorption (α sol) to thermal infrared radiation emission (ε therm). Selective surfaces take advantage of the differing wavelengths of incident solar radiation and the emissive radiation from the absorbing surface: [ 1 ]
A blackbody allows all incident radiation to pass into it (no reflected energy) and internally absorbs all the incident radiation (no energy transmitted through the body). This is true for radiation of all wavelengths and for all angles of incidence. Hence the blackbody is a perfect absorber for all incident radiation. [10]
A large drive-in RF anechoic test chamber. Note the orange caution cones for size reference. Pyramid RAM. The grey paint helps to protect the delicate radiation-absorbent material. One of the most effective types of RAM comprises arrays of pyramid-shaped pieces, each of which is constructed from a suitably lossy material. To work effectively ...
In a real-world 2008 case study [14] of large-scale cooling from increased reflectivity, it was found that the Province of Almeria, Southern Spain, has cooled 1.6 °C (2.9 °F) over a period of 20 years compared to surrounding regions, as a result of polythene-covered greenhouses being installed over a vast area that was previously open desert ...
For example, white paint absorbs very little visible light. However, at an infrared wavelength of 10×10 −6 metre, paint absorbs light very well, and has a high emissivity. Similarly, pure water absorbs very little visible light, but water is nonetheless a strong infrared absorber and has a correspondingly high emissivity.
Thermographic cameras detect radiation in the infrared range of the electromagnetic spectrum (roughly 9,000–14,000 nm or 9–14 μm) and produce images of that radiation. Since infrared radiation is emitted by all objects based on their temperatures, according to the black-body radiation law, thermography makes it possible to "see" one's ...
Researchers compressed infrared light to 10% of its wavelength using a thin strontium titanate film, paving the way for advanced infrared imaging.
The greenhouse effect on Earth is defined as: "The infrared radiative effect of all infrared absorbing constituents in the atmosphere.Greenhouse gases (GHGs), clouds, and some aerosols absorb terrestrial radiation emitted by the Earth’s surface and elsewhere in the atmosphere."