problem about semi-transparent surface

Hello, i try to make a model about semi-transparent surface by using heat transfer module. i have a point heat source and a glass material in the front of this point source, there is radiation emit by the point source, i have known the coefficient absorption and coefficient transmission, but Comsol consider the surface as opaque, so that there is not light behind the glass material.
how to solve this problem？

thank you very much!