Assuming the Sun to be a spherical body of radius R at a temperature of TK, evaluate the total radiant powered incident of Earth at a distance r from the sun
where `r_0` is the radius of the Earth and `sigma` is Stefan's constant.

Options

A. `(R^(2)sigmaT_(4))/(r^(2))`
B. `(4pir_(0)^(2)R^(2)sigmaT^(4))/(r^(2))`
C. `(pir_(0)^(2)R^(2)sigmaT^(4))/(r^(2))`
D. `(r_(0)^(2)R^(2)sigmaT^(4))/(4pir^(2))`

Answer

C

Explanation

Total radiant power incident of earth
`= ((sigma(4piR^(2))T^(4))/(4pir^(2)))pir_(0)^(2)`
(Taking sun as a block body)