Radiation that is not absorbed or scattered in the atmosphere can reach and interact with the Earth's surface. There are three (3) forms of interaction that can take place when e.m. radiation strikes, or is incident (I) upon a surface. These are: absorption, transmission, and reflection. The total incident radiation will interact with the surface in one or more of these three ways. The proportions of each will depend on the wavelength of the incident radiation and the specific chemical/physical properties of the surface material. Absorption occurs when incident radiation is absorbed into the target, while transmission occurs when radiation passes through a target. Reflection occurs when radiation "bounces" off the target and is redirected. The spectral reflectance is defined by the ratio of reflected radiance to incident radiance at a prefixed wavelegth . The spectral transmittance of a medium is defined by the ratio of the transmitted radiance to the incident one at a prefixed wavelegth . The absorbance of a medium or target is defined by the ratio of the absorbed radiance to the incident one at a prefixed wavelegth . Conservation of energy require that, at a certain wavelenght: R+T+A=1. To express the circumstance that the reflection can occurre in different direction as the surface deviates from a specular one, becoming rough, the concept of surface scattering has been introduced (ref. [PP1-2-10] The Rayleigh roughness criterion).
Illustrate basic radiation-matter interactions and related concepts of spectral reflectance, absorbance and transmittance as specific properties of the matter
Completed