Solar Luminosity: Calculating Sphere of Light Illuminating Earth's Orbit

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Homework Statement

The formula for the surface area of a sphere is 4(3.14) r2, where r is the mean distance from the sun to the earth. Determine the sphere of light (square meters) illuminated by the sun the size of the Earth's orbit.

Homework Equations

astronomical Unit-149,597,829 k

The Attempt at a Solution

my answer is 2.8122922(17)
no idea

 

[Delphi51]

Welcome to the Physics Forum, newsflash!

S = 4(3.14) r^2
= 4*3.14*(149,597,829 km)^2
= 2.81 x 10^15 km^2
If you need that in square meters, I suggest you change the r value into meters before squaring. It is tricky changing units on something after it is squared.