The solid angle subtended by the sun equals the fraction of the area of the imaginary sphere centered on earth and passing through the sun, that is occupied by the solar disk, times 47 steradians. Since the sun subtends a small solid angle, we can approximate its disk area with R and so = 4x (R/4d) = R/d. 1. Calculate the solid angle subtended by the sun using the above approximation, and compare it to the exact 0 s 2 I sin sine de do, where 0s = 0.57 is the angular diameter of the sun. 0 2. If the sun subtends a solid angle 2 on the sky, and the flux from the sun, just above the earth's atmosphere, integrated over all wavelengths, is f(do) and the flux at the solar photosphere is fphoto, then we have 4nd f(do). Using the approximation for show that fphoto = f(do)/ 4Rfphoto = equation = 3. If the solar flux at earth is f(do) = 1.4 kWm-2 use the previous result for fphoto and the Stefan-Boltzmann law to estimate the solar surface temperature.