Question

Assume that Solar constant is $1.4\, kW / m ^{2}$, radius of sun is $7 \times 10^{5} \,km$ and the distance of earth from centre of sun is $1.5 \times 10^{8} \,km$. Stefan's constant is $5.67 \times 10^{-8}\, Wm ^{-2} \,K ^{-4}$, find the approximate temperature of sun

• A. 5800 K
• B. 16000 K
• C. 15500 K
• D. 8000 K

Answer 1

Answer: (A)

$S=\left[\frac{R}{r}\right]^{2} \,\sigma \,T^{4}$
$1.4 \times 10^{3}=\left[\frac{7 \times 10^{5}}{1.5 \times 10^{8}}\right]^{2} \times 5.67 \times 10^{-8} \times T^{4}$
$T=5800\, K$