The solar constant is the amount of heat energy received per second per unit area of a perfectly black surface placed at a mean distance of the Earth form the Sun, in the absence of Earth's atmosphere, the surface being held perpendicular to the direction of Sun's rays. Its value is `1388 W//m^(2)`. If the solar constant for the earth is 's'. The surface temperature of the sun is `TK,D` is the diameter of the sun, `R` is the mean distance of the Earth from the sun. The sun subtends a small angle 'theta' at the earth. Then correct options is/are:-

Options

A. `s = sigmaT^(4) ((D)/(R ))^(2)`
B. `s =(sigmaT^(4))/(4)((D)/(R ))^(2)`
C. `s = (sigmaT^(4))/(4)theta^(2)`
D. `s=(sigmaT^(4))/(4)((R)/(D))^(2)`

Answer

B, C