Q155 / 160 · AP EAMCET 2019 (21 Apr Shift 2) · Physics

The amplitude of the electric field in a parallel beam of plane electromagnetic waves of intensity $53.1 {Wm}^{- 2}$ is
(Permittivity of free space $= 8.85 \times 10^{- 12} C^{2} N^{- 1} m^{- 2}$ )

Solution

The expression for the electromagnetic wave is,

$I = \frac{1}{2} ε_{0} E_{0}^{2} c$

Rewrite the above equation.

$E_{0} = \sqrt{\frac{2 I}{ε_{0} c}}$

Substitute the values in the above equation.

$E_{0} = \sqrt{\frac{2 \times 53.1}{8.85 \times 10^{- 12} \times 3 \times 10^{8}}} = 200 N C^{- 1}$

Hence, the correct answer is option: 'D'.