[2.12] L*(x), (at a point along a ray path)
Rate of increase in radiance, per unit path length, at the point and in the direction of the ray, due to “generated” (emitted or scattered) radiance, or the “generated” radiant intensity per unit volume, at the point and in the direction of the ray, by which a distributed source can be characterized.
L* = dLg /dx = dIg /dV, where dx is an element of distance along the ray path, dV is an element of volume at the point, and the subscript g denotes a “generated” quantity.
Note: This quantity is useful in dealing with radiative transfer through a region where significant emission or scattering into the ray, as well as attenuation by absorption or scattering out of the ray, occurs along a ray path; also for evaluating the intensity of an extended volume of emitting and partially transmitting (transparent) material. This is discussed in more detail on pp. 41-45 of NBS Technical Note 910-2.*
* Self Study Manual on Optical Radiation Measurements; Part 1 – Concepts; Chapters 4 and 5, NBS Technical Note 910-2. Washington, DC: U.S. Department of Commerce. Feb. 1978.« Back to Definitions Index