| More Terms
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- Along with brightness, radiance, radiant flux, etc., several more terms are needed to discuss the interaction of radiation with matter. These terms are: Reflectance, Transmittance, Absorptance, Emissivity
- Hemispherical terms
These terms are needed because surfaces viewed by a sensor are illuminated by the sun or an active instrument, and the incident flux density (irradiance) is either reflected, absorbed or transmitted through the surface. The reflected portion allows the object to be sensed.
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Hemispheric Reflectance Ratio of the reflected emittance to the incident irradiance, ρ = Mρ/E
Hemispheric Transmittance Ratio
of the transmitted emittance to the incident irradiance,τ = M τ/E
Hemispheric Absorptance Ratio of the absorbed flux density to the incident irradiance, α = M α/E
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| Energy interactions with earth surface features
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| When EMR is incident on any given earth surface feature, three fundamental energy interactions with the feature are possible:
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- Reflection
- Absorption
- Transmission
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| The relationship between these three energy interactions is given by the Principle of conservation of energy
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| Principle
of conservation of energy
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