Let us assume that sun radiates like a black body with surface temperature at `T_0=6000K` and earth absorbs radiation coming from sun only. If both earth and sun are considered perfect spheres with distance between centre of earth and centre of sun to be 200 times the radius of sun, find the temperature (in Kelvin) of surface of earth in steady state (assume radiation incident on earth to be almost parallel).

Explanation

Power absorbed by earth`=`power emitted by earth.
`(esigma(4piR_S^2)T_S^4)/(4pir^2)xxpiR_e^@=esigma(4piR_e^2)T_e^4`
`T_e=T_Ssqrt((R_S)/(2r))=T_Ssqrt((R_S)/(2xx200R_S))`
`T_C=(T_S)/(20)=300K`