The solar constant for the earth is about `1.8J//m^(2)//s`. What is the solar constant for a black body situated on a planet which is situated at a distance of 0.3 times the distance of the earth from the sun ?

Options

A. `9J//m^(2)//s`
B. `12J//m^(2)//s`
C. `15J//m^(2)//s`
D. `20J//m^(2)//s`

Answer

D

Explanation

Solar constant is the radiant energy received per unit area of the surface of the earth per unit time. But the incident radiant energy per second depends upon the distance between the sun and the planet as
`"Intensity"prop1/("Distance")^(2)`
`thereforeI_(2)/I_(1)=r_(1)^(2)/r_(2)^(2)=r_(1)^(2)/(3r_(1))^(2)=100/9` as `sprop1`
`therefores_(2)/s_(1)=I_(2)/I_(1)=100/9`
`thereforeS_(2)=100/9s_(1)=100/9xx1.8=20`