Thermal emission of a disc body of semitransparent material

By introducing the concept of radiosity intensity to diffuse surfaces, the ray tracing method is improved to analyze the thermal emission of a disc body of gray semitransparent material. The two plane surfaces of the disc body are both specularly reflecting, and the flank surface is either diffusely reflecting or specularly reflecting. The apparent thermal emission from one plane surface is investigated with considering the influences of the characteristic optical thickness, the dimensionless radius, the refractive index of the material and the reflecting characteristics of the flank surface. The directional and hemispherical emissions show considerable differences under different reflecting characteristics of the flank surface. Moreover, in some cases, the emission not only varies with the viewing direction but also with the apparent emitting position on the plane surface. Some interesting results are presented and discussed.