Imagine a closed isolated system consisting of 2 rooms separated by a window. The window is built with one layer of material that has refractive index 1.5 and one layer of material that has refractive index 2, for a wide range of wavelenghts (say 1 [tex]\mu[/tex] m - 50 [tex]\mu[/tex] m), and low absorption. The side with lower refractive index is in room A, the side with higher refractive index is in room B. Alice is standing in room A and Bob is standing in room B. Alice and Bob radiate electromagnetic waves with power [tex]\sigma A T^4 [/tex] (Stefan–Boltzmann law) with wavelengths almost entirely in the range 1 [tex]\mu[/tex] m - 50 [tex]\mu[/tex] m (Planck's law). An easy calculation using Fresnel equations shows that more radiation is transmitted through the window from room A to room B than from room B to room A. So Alice should get colder and Bob warmer. Where is the mistake?