The correct answer is **1,368 MW/km ^{2}**:

1,000,000 W = 1 MW, so 1,368 W/m^{2} = 0.001368 MW/m^{2}

1,000 m = 1 km

But 1,000,000 m^{2} = 1 km^{2}: One square kilometer is the area of a square one kilometer on a side. That is a square 1,000 meters by 1,000 meters, or an area of 1,000,000 square meters. So 0.001368 MW for each m^{2} times 1,000,000 m^{2} = 1,368 MW for each km^{2}.

**Question 2.**

We will work in W/m^{2}. About 22% of the flux (1,368 W/m^{2}) is absorbed or reflected by the Earth's atmosphere before it reaches the ground (even ignoring clouds). How much power per square meter is left?

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© 2001-2002, 2005 by Wm. Robert Johnston.

Last modified 11 January 2005.

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