A horizontal semitransparent plate is uniformly irradiated from above and below, while air at T? = 300 K flows over the top and bottom surfaces, providing a uniform convection heat transfer coefficient of h = 40 W/m2 ? K. The total, hemispherical absorptivity of the plate to the irradiation is 0.40. Under steady-state conditions measurements made with a radiation detector above the top surface indicate a radiosity (which includes transmission, as well as reflection and emission) of J = 5000 W/m2, while the plate is at a uniform temperature of T = 350 K. Determine the irradiation G and the total hemispherical emissivity of the plate. Is the plate gray for the prescribed conditions?

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Detector Semitransparent plate, T T h G.