Question

The sun radiates electromagnetic energy at the rate of $3.9\times {10}^{26}W$. Its radius is $6.96\times {10}^{8}m$. If the distance from the sun to the earth is $1.5\times {10}^{11}m$, then the intensity of sunlight on earth's surface will be (in $W/m^2$):

• A. $1.38\times {10}^3$
• B. $2.76\times {10}^4$
• C. $5.52\times {10}^5$
• D. None of these

Answer 1

The correct option is A $1.38\times {10}^3$

Intensity of sunlight at earth surface, $I=\frac{Rateofenergyradiated}{4\pi R^2}$ where $R$ is the distance of earth from sun.

$I=\frac{3.9\times {10}^{26}}{4\pi \times [1.5\times {10}^{11}{]}^2}$

$⟹I=1.38\times {10}^{3}W/m^2$