Question

In an electromagnetic wave, the maximum value of the electric field is $100 \, Vm^{- 1}$ . The average intensity is [ $\epsilon _{0}=8.8\times 10^{- 12}C^{- 2}N^{- 1}m^{2}$ ]

• A. $13.2Wm^{- 2}$
• B. $36.5 \, W \, m^{- 2}$
• C. $46.7 \, W \, m^{- 2}$
• D. $765 \, W \, m^{- 2}$

Answer 1

Answer: (A)

$I_{avg}=\frac{1}{2}c\left(\epsilon \right)_{0}\left(E_{0}\right)^{2}$
$\Rightarrow I_{avg}=\frac{1}{2}\times 3\times \left(10\right)^{8}\times 8.8\times \left(10\right)^{- 12}\times \left(100\right)^{2}$
$\Rightarrow I_{avg}=13.2Wm^{- 2}$