where nr is the refractive index (dimensionless), σ is the Stefan-Boltzmann constant (SI unit: W/(m2·K4)), and βR is the extinction coefficient.

This section is available when material properties are temperature-dependent. By default, the temperature of the parent interface is used and the section is not editable. To edit the Temperature field, click Make All Model Inputs Editable (). The available options are User defined (default), Common model input (the minput.T variable, set to 293.15 K by default) and all temperature variables from the physics interfaces included in the model. To edit the minput.T variable, click the Go to Source button (), and in the Default Model Inputs node under Global Definitions, set a value for the Temperature in the Expression for remaining selection section.

First, define the Refractive index nr (dimensionless) of the participating medium.The default value, 1, is usually a good approximation for the air refractive index.

Then, depending on the available quantities, the extinction coefficient βR can be specified directly or defined as the sum of the absorption and scattering coefficients. Also see Rosseland Approximation Theory.

The following options are available from the Specify media properties list:

This section defines the absorption property of the participating medium. It is available when Absorption and scattering coefficients is selected from the Specify media properties list. The Absorption coefficient κ should be specified. It defines the amount of radiation, κI(Ω), that is absorbed by the medium.

This section defines the scattering property of the participating medium, and is available when Absorption and scattering coefficients is selected from the Specify media properties list. The Scattering coefficient σs should be specified.

Physics Tab with Solid, Fluid, Porous Medium, Biological Tissue, or Building Material selected in the model tree: