Why do materials have different Emissivity and Absorptivity?
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I read this
Problem on Emissivity and absorptivity but I am still wondering, why for example "white paint is quoted as having an absorptivity of 0.16, while having an emissivity of 0.93"
According to Kirchhoffs Law, absorptivity = emissivity coefficient (for all wavelengthts in Equilibrium temperature.
it is a little bit explained, but I still do not get it.
So if I plot the emissivity and aborptivity of my white paint for T=300K over all wavelenghts for a given temperature, then they should match identical? If I raise the temperature to T=350 K the shape will Change, but both will be identical.
So how comes, that they have different values? I guess, that the emissivity depends on the body's temperature, whereas the absorptivity depends on the temperature of the surrounding/sun . But still, a Body should have the same radiative characteristics according to Kirchhoff
Problem on Emissivity and absorptivity but I am still wondering, why for example "white paint is quoted as having an absorptivity of 0.16, while having an emissivity of 0.93"
According to Kirchhoffs Law, absorptivity = emissivity coefficient (for all wavelengthts in Equilibrium temperature.
it is a little bit explained, but I still do not get it.
So if I plot the emissivity and aborptivity of my white paint for T=300K over all wavelenghts for a given temperature, then they should match identical? If I raise the temperature to T=350 K the shape will Change, but both will be identical.
So how comes, that they have different values? I guess, that the emissivity depends on the body's temperature, whereas the absorptivity depends on the temperature of the surrounding/sun . But still, a Body should have the same radiative characteristics according to Kirchhoff
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Nonmetallic (high E) materials with surface electrons strongly coupled to atoms below them can absorb IR energy.
This is why emissive materials both absorb and emit energy well. Wavelengths vs Emissivity/Absorptivity. Antennas have a physical length equal to a fractional multiple of the signal wavelength or period.
This is why emissive materials both absorb and emit energy well. Wavelengths vs Emissivity/Absorptivity. Antennas have a physical length equal to a fractional multiple of the signal wavelength or period.
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