Abstract
Modern illuminating engineering has frequently to do with installations consisting of a long row of mutually identical luminaries or of a number of such long rows. It is proved in this article that the average illumination, which is caused by a long row of luminaries on a line parallel to the row, can be determined directly and rather easily, when the geometrical situations is known and the light-intensity distribution of the applied luminaire is related to bundle planes through the luminaire row. The calculation method has been demonstrated on an example of a practical installation, for which the caused illumination had to be predicted.