Apparent emissivity of an absorbing-emitting-scattering semitransparent slab with variable spatial refractive index

A backward Monte Carlo curved ray-tracing method is developed to analyze the apparent emissivity of one-dimensional absorbing-emitting-scattering semitransparent slab with variable spatial refractive index. An isothermal semitransparent slab with linear variable spatial refractive index is taken as an example to examine the accuracy of the proposed method. The directional apparent emissivity is determined by the proposed method and compared with the data in references, and the effects of the single scattering albedo and the scattering phase function on the directional apparent emissivity are analyzed. The results show that the backward Monte Carlo curved ray-tracing method has a good accuracy in solving the apparent emissivity of semitransparent slab with variable spatial refractive index, and converges more quickly than the forward Monte Carlo method. The effect of single scattering albedo is significant and the influence of the scattering phase function is similar to that of the slab with constant refractive index.