On a cloudless day, the sunlight that reaches the surface of the earth has an intensity of about 1.2 103 W/m2. What is the electromagnetic energy contained in 6.4 m3 of space just above the earth's surface?

Answer 1

V= 6.3m³= A•h =1m•1m• 6.3 m

t=h/c=6.3/3•10⁸=2.1•10⁻⁸s.
Energy hitting the base of 1m² is
E₀=I/A=1.2•10³(W/m²)/1(m²)=
= 1.2•10³ W = 1.2•10³ W J/s.

E=E₀•t=1.2•10³(J/s) •2.1•10⁻⁸(s) =
=2.52•10⁻⁵ J