\[d_1 = 147.1\]
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
\[\frac{I}{d_2^2} = \frac{3.846 \times 10^{26|}}{4 \pi (152.1 \times 10^6)^2} = 1.323 W/m^2\]