Measurement of Spectral Reflectance and Emissivity of Specular and Diffuse Surfaces in the Carbon Arc Image Furnace

Abstract

Basically, there are two ways of measuring the spectral emissivity of the surface of an opaque body. One widely used method involves the direct measurement of the spectral radiance of the surface along with a determination of its temperature. Combination of these data with the blackbody radiation laws yields the spectral emissivity. Another method measures the spectral reflectance of the surface. From this, the spectral absorptance is calculated and, by application of Kirchhoff’s law, is equated to the spectral emissivity. Both of these methods, which we shall designate respectively as the “radiation” and “reflection” methods, have their limitations, which will receive attention in this paper.