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)

1020 N C^-1

$ 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$