Absorptance - Alchetron, The Free Social Encyclopedia

Absorptance of the surface of a material is its effectiveness in absorbing radiant energy. It is the fraction of incident electromagnetic power that is absorbed at an interface, in contrast to the absorption coefficient, which is the ratio of the absorbed to incident electric field. This should not be confused with absorbance.

Hemispherical absorptance

Hemispherical absorptance of a surface, denoted A, is defined as

A = Φ e a Φ e i ,

where

Φ_e^a is the radiant flux absorbed by that surface;

Φ_eⁱ is the radiant flux received by that surface.

Spectral hemispherical absorptance

Spectral hemispherical absorptance in frequency and spectral hemispherical absorptance in wavelength of a surface, denoted A_ν and A_λ respectively, are defined as

A ν = Φ e , ν a Φ e , ν i , A λ = Φ e , λ a Φ e , λ i ,

where

Φ_e,ν^a is the spectral radiant flux in frequency absorbed by that surface;

Φ_e,νⁱ is the spectral radiant flux in frequency received by that surface;

Φ_e,λ^a is the spectral radiant flux in wavelength absorbed by that surface;

Φ_e,λⁱ is the spectral radiant flux in wavelength received by that surface.

Directional absorptance

Directional absorptance of a surface, denoted A_Ω, is defined as

A Ω = L e , Ω a L e , Ω i ,

where

L_e,Ω^a is the radiance absorbed by that surface;

L_e,Ωⁱ is the radiance received by that surface.

Spectral directional absorptance

Spectral directional absorptance in frequency and spectral directional absorptance in wavelength of a surface, denoted A_ν,Ω and A_λ,Ω respectively, are defined as

A ν , Ω = L e , Ω , ν a L e , Ω , ν i , A λ , Ω = L e , Ω , λ a L e , Ω , λ i ,

where

L_e,Ω,ν^a is the spectral radiance in frequency absorbed by that surface;

L_e,Ω,νⁱ is the spectral radiance received by that surface;

L_e,Ω,λ^a is the spectral radiance in wavelength absorbed by that surface;

L_e,Ω,λⁱ is the spectral radiance in wavelength received by that surface.

References

Absorptance Wikipedia

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Contents

Hemispherical absorptance

Spectral hemispherical absorptance

Directional absorptance

Spectral directional absorptance

References