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 distance R from the centre of the Sun is:-
Where `sigma` is the Stefan's Constant.

Options

A. 2 R
B. `2^(5//3)R`
C. `2^(4//3)R`
D. 3 R

Answer

C

Explanation

heatcurrent `=(4T-2T)/(((ln(r//R))/(2piKL)))=(2T-T)/(((ln(4R//r))/(2piKL)))`
`2ln((4R)/(r))=ln((r)/(R))`

`((4R)/(r))^(2)=(r)/(R)rArrr^(3)=16R^(3)r=2^(4//3)R`