Use this node to model an absorbing medium’s boundary where there is no radiative intensity absorption. All the outgoing beams traveling from the medium to the exterior leave the media without depositing any energy at this boundary. The intensity of radiative beams entering the absorbing media is set to zero. See Opaque Surface (Radiative Beam in Absorbing Medium Interface) to take into account radiative intensity absorption on boundaries.

Physics tab with Radiative Beam in Absorbing Media selected: