## Intensity of Sun's Radiation Reaching Earth

The distance between the Earth and the Sun varies between
$d_1 = 147.1$
and
$d_2 = 152.1$
million km.
The luminosity of the Sun - the total power output - is
$I=3.846 \times 10^{26}$
W.
This means that the intensity of the Sun's radiation reaching the Earth varies between
$\frac{I}{4 \pi d_1^2} = \frac{3.846 \times 10^{26|}}{4 \pi (147.1 \times 10^6)^2} = 1414 W/m^2$

and
$\frac{I}{d_2^2} = \frac{3.846 \times 10^{26|}}{4 \pi (152.1 \times 10^6)^2} = 1.323 W/m^2$