Two very thick dielectric regions with small absorption coefficients are separated by a plane…

Two very thick dielectric regions with small absorption coefficients are separated by a plane layer of a third dielectric material that is of thickness D = 2 cm. The two interfaces are optically smooth. The plane layer between the two thick regions is perfectly transparent. This plane layer is at low temperature, having been suddenly inserted between the two dielectric regions. For the temperatures shown, calculate the net heat flux being transferred by radiation from medium 1 into medium 2. Include the effects of interface reflections. The effect of heat conduction is neglected. The indices of refraction are given in the figure.