First slide

Electromagnetic waves and its nature

Question

The amplitude of the electric field in a parallel beam of plane electromagnetic waves of intensity $106.2 W m^{- 2}$ is (permittivity of free space= $8.85 \times 10^{- 12} C^{2} / N m^{2}$ )

Moderate

A

$\sqrt{2} \times 10^{2} V m^{- 1}$
B

$2 \sqrt{2} \times 10^{2} V m^{- 1}$
C

$\frac{1}{\sqrt{2}} \times 10^{2} V m^{- 1}$
D

$10^{2} V m^{- 1}$

Solution

Intensity of electromagnetic wave in terms of maximum electric field is
$I = \frac{1}{2} \in_{0} E_{0}^{2} C \Rightarrow E_{0} = \sqrt{\frac{2 I}{\in_{0} C}} \Rightarrow E_{0} = \sqrt{\frac{2 \times 106.2}{8.85 \times 10^{- 12} \times 3 \times 10^{8}}} = 2 \sqrt{2} \times 10^{2} V / m$

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