Generalized angle factor of radiation

Ratio of the radiant flux leaving the surface (area element) of a given body and arriving at the surface (area element) of another body, taking into account attenuation of the radiation by the intermediate medium, to the hemispherical flux of natural radiation leaving the surface of the given body.

Comments. 1. We distinguish between "elemental," "local" and "average" generalized angle factors of radiation.
2. The radiating bodies are assumed to be black.