The energy flux associated with solar radiation incident on the outer surface of the earth’s atmosphere has been accurately measured and is known to be 1368 W/m2. The diameters of the sun and earth are 1.39 × 109 and 1.27 × 107 m, respectively, and the distance between the sun and the earth is 1.5 × 1011 m. (a) What is the emissive power of the sun? (b) Approximating the sun’s surface as black, what is its temperature? (c) At what wavelength is the spectral emissive power of the sun a maximum? (d) Assuming the earth’s surface to be black and the sun to be the only source of energy for the earth, estimate the earth’s surface temperature.