Answer:
[tex]I=2.67\times 10^{-6}\ W/m[/tex]
Explanation:
Given that,
Frequency of a radio antenna is 1 MHz
Power, P = 21 kW
We need to find the the waves intensity 25 km from the antenna . The object emits intenisty evenly in all direction. It can be given by :
[tex]I=\dfrac{P}{4\pi r^2}\\\\I=\dfrac{21\times 10^3}{4\pi (25000)^2}\\\\I=2.67\times 10^{-6}\ W/m[/tex]
So, the wave intensity 25 km from the antenna is [tex]2.67\times 10^{-6}\ W/m[/tex].
