Question

Assuming the sun to have a spherical outer surface of radius r, radiating like a black body at temperature $t^{\circ} C$, 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.

• A. $r^2 \sigma (t + 273)^4 /R^2$
• B. $4 \pi r^2 \sigma t^4 / R^2$
• C. $r^2 \sigma (t + 273)^4 / 4\pi R^2$
• D. $16 \pi^2 r^2 \sigma t^4 / R^2$

Answer 1

Answer: (A)

$r^2 \sigma (t + 273)^4 /R^2$

Answer 2

Solar constant $=\frac{\sigma\left(4 \pi r ^{2}\right) T ^{4}}{\left(4 \pi R ^{2}\right)}=\frac{\sigma r^{2}( t +273)^{4}}{ R ^{2}}$