Abstract
The shadow is a phenomenon which reduces the illuminance on an illuminated plane, because the light is obscured by an object interposed between a light source and an illuminated plane. Therefore, when viewing the light source from the illuminated point in the shadow, all or a part of light source is obscured by the object.
For, calculating the illuminance values in the shadow, it is necessity to consider only the part of light source which can be viewed practically from an illuminated point.
This paper describes the method of calculating the illuminance in the shadow, and the results of the experiments under the condition that the diffused linear light source is kept in a horizontal or vertical position and the horizontal disk is used as an object by which the shadow is formed.
And the calculated values was confirmed experimentally.
