1. The problem statement, all variables and given/known data Given the following info: Solar output(modulus of the Poynting vector): [itex]1.4kW/m^2[/itex] Earth radius: 6370km Average Earth orbit radius: [itex]1.49*10^11 m[/itex] Find the total power output of the Sun, power received on the Earth, and the power received in Spain if its surface area is 5*10^2 km^2 and is at a latitude of 40 N. 2. Relevant equations Poynting vector formula? 3. The attempt at a solution I managed to get the right answer for the power received on the Earth, but I'm not sure how to proceed with the other 2 questions. Wouldn't the power received at a given latitude depend on the time of the year? I found this applet that calculates it for you and apparently at 40 N, the solar output never reaches 1.4kW at any time of the year: http://pvcdrom.pveducation.org/SUNLIGHT/SHCALC.HTM ... so I'm guessing I'll have to resort to spherical trigonometry some way or another? I am given no other info and this is a course purely on electromagnetic optics.