Question

The RMS value of the electric field of an electromagnetic wave emitted by a source is \( 660 \) N/C. The average energy density of the electromagnetic wave is:

• A. \( 1.75 \times 10^{-6} \) J/m\(^3\)
• B. \( 2.75 \times 10^{-6} \) J/m\(^3\)
• C. \( 4.85 \times 10^{-6} \) J/m\(^3\)
• D. \( 3.85 \times 10^{-6} \) J/m\(^3\)

Hint:

The energy density of an electromagnetic wave is given by \( u = \frac{\varepsilon_0 E_{\text{rms}}^2}{2} \).

Answer 1

The Correct Option is D

Step 1: Apply Energy Density Formula The average energy density is given by: \[ u = \frac{\varepsilon_0 E_{\text{rms}}^2}{2} \] Step 2: Compute Energy Density \[ u = \frac{(8.85 \times 10^{-12}) (660)^2}{2} \] \[ u = 3.85 \times 10^{-6} \text{ J/m}^3 \] Thus, the correct answer is \( 3.85 \times 10^{-6} \) J/m³.