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we used a value of 1380 W/m^2 for the intensity (power per unit area) of radiati

ID: 1371972 • Letter: W

Question

we used a value of 1380 W/m^2 for the intensity (power per unit area) of radiation arriving at the earth from the sun. Using the Stefan-Boltzman Law. Assume that the sun is a black body at a temperature of 5778K and it has a radius of 6.955×105 km.

1. What is the total EM power emitted by the sun?

2. Now imagine that the power calculated in 1 is distributed equally over the surface of a sphere with a radius equal to the average earth-sun distance (1.496 ×108 km). What is the power per unit area?

Explanation / Answer

I =1380 W/m^2, R =6.955x10^5 km

I =P/A

P =IA = (I)(4pi*R2)

P =(1380)(4x3.14x(6.955x108)2)]

P =8.38x1013 W