Answer:
Power emitted will be 0.314 mW
So option (A) will be correct option
Explanation:
We have given threshold hearing [tex]I=10^{-12}W/m^2[/tex]
Distance is given r = 5 km =5000 m
We have to find the power emitted
Power emitted is equal to
[tex]P=I\times A[/tex]
[tex]=10^{-12}\times 4\pi r^2[/tex]
[tex]=10^{-12}\times 4\times 3.14\times (5000)^2[/tex]
=[tex]314\times 10^{-6}watt=0.314mW[/tex]
So power emitted will be 0.314 mW
So option (A) will be correct option.