Question

In an electromagnetic wave in free space the root mean square value of the electric field is $E_{rms} = 6V/m^{-1}$. The peak value of the magnetic field is :

• A. $2.83 \times 10^{-8} T $
• B. $0.70\times 10^{-8} T $
• C. $4.23 \times 10^{-8} T $
• D. $1.41 \times 10^{-8} T $

Answer 1

Answer: (A)

$\frac{E_{ rms }}{B_{ rms }} =c$
$B_{ rms } =\frac{E_{ rms }}{c}$
$=\frac{6}{3 \times 10^{8}}$
$B_{ rms } =2 \times 10^{-8}$
$B_{ rms } =\frac{B_{0}}{\sqrt{2}}$
$B_{0}= \sqrt{2} \times B_{ rms }$
$=\sqrt{2} \times 2 \times 10^{-8}$
$=2.83 \times 10^{-8} T$