Question

At the threshold of detection, an FM receiver can pick up a signal for which $E_0=2\mu \text{V/m}$. The intensity of the electromagnetic wave is -

• A. $5.31\times {10}^{-15}{\text{W-m}}^{-2}$
• B. $5.31\times {10}^{-12}{\text{W-m}}^{-2}$
• C. $5.31\times {10}^{-14}{\text{W-m}}^{-2}$
• D. $5.31\times {10}^{-17}{\text{W-m}}^{-2}$

Answer 1

The correct option is A $5.31\times {10}^{-15}{\text{W-m}}^{-2}$

Intensity of an electromagnetic wave is given by,

$I=\frac{1}{2}{ϵ}_0{E}_0^{2}c$

$\Rightarrow I=\frac{1}{2}\times 8.85\times {10}^{-12}\times {(2\times {10}^{-6})}^2\times 3\times {10}^8$

$\Rightarrow I=5.31\times {10}^{-15}{\text{W-m}}^{-2}$

Hence, option $\left(A\right)$ is the correct answer.