Answer:
various parts have been answered
Explanation:
Inverse square for light is [tex]I_1r_1^2=I_2r_2^2[/tex]
initial distance from sun to earth is[tex]r_1=150\times10^6 [/tex]
and intensity or apparent brightness of sun is [tex]I_1=1300\ W/m^2[/tex]
a)
If distance from sun to earth is [tex]r_2=r_1/2=\frac{150\times10^6}{2}[/tex]
then apparent brightness is [tex]I_2=\frac{I_1r_1^2}{r_2^2}=\frac{1300\times r_1^2}{(r_1/2)^2}=5200[/tex]
b)
If distance from sun to earth is [tex]r_2=2r_1[/tex]
then apparent brightness is [tex]I_2=\frac{I_1r_1^2}{r_2^2}=\frac{1300\times r_1^2}{(2r_1)^2}=325\,W/m^2[/tex]
c)
If distance from sun to earth is [tex]r_2=7r_1[/tex]
then apparent brightness is
[tex]I_2=\frac{I_1r_1^2}{r_2^2}=\frac{1300\times r_1^2}{(7r_1)^2}=26.5\,W/m^2[/tex]
