Question

The electric field in an electromagnetic wave is given by $E = 56.5\ sin ω(t – \frac xc)\ NC^{–1}$. Find the intensity of the wave if it is propagating along x-axis in the free space. (Given $∈_0 = 8.85 × 10^{–12} C^2N^{–1}m^{–2}$)

• A. $5.65\ Wm^{–2}$
• B. $4.24\ Wm^{–2}$
• C. $1.9 × 10–7\ Wm^{–2}$
• D. $56.5\ Wm^{–2}$

Answer 1

Answer: (B)

$4.24\ Wm^{–2}$

Answer 2

Intensity of the wave,
$I = \frac 12ε_0E^2_0c$
$I = \frac 12 \times 8.5 \times 10^{-12} \times (56.5)^2 \times 3 \times 10^8$
$I= 4.24\ w/m^2$

So, the correct option is (B): $4.24\ Wm^{–2}$