It is a well-known fact that the graphic forms of the apparent directional emittances of the metallic and the nonmetallic rough surfaces，indicated in polar co-ordinates，are different from those of the flat smooth surfaces of the same kinds．A theoretical analysis of the apparent directional emittances of the metallic and the nonmetallic random rough surfaces was performed， assuming the roughness of those surfaces was composed of various sorts of circular arc grooves distributed regularly at a fixed rate. The apparent directional emittances were calculated applying the emissive characteristics given by the approximate formula introduced by E.Schmidt and other for metals and applying Fresnel’s formula for nonmetals to the inside surface of the groove. The apparent directional emittances of the metallic rough surfaces of aluminum and brass scratched with various grain sized sandpapers and the nonmetallic rough surfaces coated with the asbestos mixture paints ｗere measured，and the result of the theoretical analysis was coｍpared with the experimental result.
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