The intensity of a plane monochromatic wave is 1380 Wm-2. What is the amplitude of electric field in this wave? (Take speed of light 3 × 108 ms-1; ε0 = 8.85 × 10-12 C2N-1m-2)
Answer & explanation
Correct answer: option 3
$ I = \frac{1}{2} \epsilon_0 c E_0^2 = 1380 $
$\Rightarrow E_0^=2 = \frac{2760}{8.85\times 10^{-12}\times 3\times 10^8} = 1.04\times 10^6$
$ E_0 = 1.02\times 10^3 = 1020 N/C$