The directional absorptivity of a gray surface varies with ? as follows.

(a) What is the ratio of the normal absorptivity an to the hemispherical emissivity of the surface?

(b) Consider a plate with these surface characteristics on both sides in earth orbit. If the solar flux incident on one side of the plate is q''S = 1353 W/m2, what equilibrium temperature will the plate assume if it is oriented normal to the sun's rays? What temperature will it assume if it is oriented at 75° to the sun's rays?

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0.9 0= 60° O 0.1