- #1
Chowie
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Homework Statement
An astronomer is trying to estimate the surface temperature of a star with a radius of 5.0*10^8m by modeling it as an ideal blackbody. The astronomer has measured the intensity of radiation due to the star at a distance of 2.5*10^13m and found it to be equal to 0.055W/m^2 . Given this information, what is the temperature of the surface of the star?
Express your answer in kelvins to two significant digits.
Homework Equations
I is proportional to Stefans constant * Temp to the power of 4
Surface intensity = Intensity measured from a distance * (Distance / Radius)^2
The Attempt at a Solution
With those two equations above the answer itself just falls out, however I only found the second equation while looking around for help on this question.
Can anyone explain to me in English why the second equation holds true? Is it already in its simplest form and I should just remember it?
Cheers