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

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