Assuming the sun to have a spherical outer surface of radius `r` radiating like a black body at temperature `t^(@)C`. The power received by a unit surface (normal to the incident rays) at a distance `R` from the centre of the sun is
where `sigma` is the Stefan's constant.

Options

A. `r(2) sigma (t+273)^(4)//R^(2)`
B. `4 pi r^(2) sigmat^(4)//R^(2)`
C. `r^(2) sigma (t+273)^(4)//4piR^(2)`
D. `16pi^(2)r^(2) sigma t^(4)//R^(2)`

Answer

A

Explanation

Solar constant `=(sigma(4 pir^(2))T^(4))/((4piR^(2)))=(sigmar^(2)(t+273)^(4))/(R^(2))`