A small flat plate is positioned just beyond the earth's atmosphere and is oriented such that the normal to the plate passes through the center of the sun. Refer to Problem 12.20 for pertinent earth-sun dimensions.

  (a) What is the solid angle subtended by the sun about a point on the surface of the plate?

  (b) Determine the incident intensity, I_i, the plate using the known value of the solar irradiation above the earth's atmosphere (G_s = 1353 W/m²).

  (c) Sketch the incident intensity I_i as a function of the zenith angle θ, where θ is measured from the normal to the plate.