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Low emissivity (low e or low thermal emissivity) refers to a surface condition that emits low levels of radiant thermal (heat) energy. All materials absorb, reflect, and emit radiant energy according to Planck's law but here, the primary concern is a special wavelength interval of radiant energy, namely thermal radiation of materials. In common ...
The basic measure of PDRCs is their solar reflectivity (in 0.4–2.5 μm) and heat emissivity (in 8–13 μm), [2] to maximize "net emission of longwave thermal radiation" and minimize "absorption of downward shortwave radiation". [5]
The IPCC reports an outgoing thermal radiation flux (OLR) of 239 (237–242) W m-2 and a surface thermal radiation flux (SLR) of 398 (395–400) W m-2, where the parenthesized amounts indicate the 5-95% confidence intervals as of 2015. These values indicate that the atmosphere (with clouds included) reduces Earth's overall emissivity, relative ...
Thermal emittance or thermal emissivity is the ratio of the radiant emittance of heat of a specific object or surface to that of a standard black body.Emissivity and emittivity are both dimensionless quantities given in the range of 0 to 1, representing the comparative/relative emittance with respect to a blackbody operating in similar conditions, but emissivity refers to a material property ...
Thermal radiation is the emission of electromagnetic waves from all matter that has a temperature greater than absolute zero. [5] [2] Thermal radiation reflects the conversion of thermal energy into electromagnetic energy. Thermal energy is the kinetic energy of random movements of atoms and molecules in matter. It is present in all matter of ...
Thermionic emission is the liberation of charged particles from a hot electrode whose thermal energy gives some particles enough kinetic energy to escape the material's surface. The particles, sometimes called thermions in early literature, are now known to be ions or electrons .
Kirchhoff's law of thermal radiation has a refinement in that not only is thermal emissivity equal to absorptivity, it is equal in detail. Consider a leaf. It is a poor absorber of green light (around 470 nm), which is why it looks green. By the principle of detailed balance, it is also a poor emitter of green light.
For low clouds, the reflection of solar radiation is the larger effect; so, these clouds cool the Earth. ... then thermal emissions to space will be reduced ...