Answer:
[tex]B_2=2.1nT[/tex]
Explanation:
From the question we are told that:
Frequency [tex]F=800kHz[/tex]
Distance [tex]d=4.5km[/tex]
Electric field amplitude [tex]B_2=0.63V/m[/tex]
Generally the equation for momentum is mathematically given by
[tex]B=\frac{E}{C}[/tex]
Therefore
[tex]B_2=\frac{0.63}{3*10^8}[/tex]
[tex]B_2=0.21*10^{-8}[/tex]
[tex]B_2=2.1nT[/tex]