Question

If temperature of Sun = 6000K, radius of Sun is 7.2 × 10⁵ Km, radius of Earth = 6000 Km & distance between earth and Sun = 15 × 10⁷ Km. Find intensity of light on Earth.

• A. 19.2 × 10¹⁶
• B. 12.2 × 10¹⁶
• C. 18.3 × 10¹⁶
• D. 9.2 × 10¹⁶

Answer 1

Answer: (A)

Total energy emitted by Sun = $\sigma$T⁴ × 4$\pi$R²
Energy received by earth $=\frac{\sigma T^{4}4\pi R_S^{{}^2}}{4\pi d^2}\times \pi {\left(Re\right)}^2$
$=\frac{\sigma T^4{R}_{{}_s}^{{}^2}}{d^2}\times \pi {\left(Re\right)}^2$
$=\frac{5.67\times 10^{-8}\times {\left(6000\right)}^4\times {\left(7.2\times 10^8\right)}^2\times 3.14\times \left(6000\times 10^3\right)}{{\left(1.5\times 10^{11}\right)}^2}$
$=\frac{5.67\times 36\times 36\times 7.2\times 7.2\times 36\times 3.14}{2.25}\times 10^{10}=19.2\times 10^{16}$