This chapter explains some of the basics of radiative transfer, and it provides explanations of some of the concepts that are related to the transfer of radiation among and between surfaces and optical systems.
3.1 The Fundamental Equation of Radiative Transfer
The transfer of radiation in a vacuum environment from one surface to another, no matter how complicated the two surfaces, can be described succinctly by the differential form of the fundamental equation of radiative transfer. It is dÎ¦=LdA1cosÎ¸1dA2cosÎ¸2Ï2, where L can be the radiance from either surface to the other, or the net radiance, A is an area, Î¸ is the angle between a surface normal and the line of sight between the surfaces, Ï is the line-of-sight distance, and the subscripts indicate the first and second surfaces. This is illustrated in Figure 3-1.
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