Electromagnetic Waves Ques 23
23. In an electromagnetic wave in free space the root mean square value of the electric field is $E _{rms}=6 $ $V / m$. The peak value of the magnetic field is :-
[2017]
(a) $2.83 \times 10^{-8} T$
(b) $0.70 \times 10^{-8} T$
(c) $4.23 \times 10^{-8} T$
(d) $1.41 \times 10^{-8} T$
Show Answer
Answer:
Correct Answer: 23.(a)
Solution:
- (a) Given, $E _{rms}=6$ $ V / m$
$\frac{E _{rms}}{B _{rms}}=c$
$\Rightarrow B _{rms}=\frac{E _{rms}}{c}$ $\quad$ …….(i)
$B _{rms}=\frac{B_0}{\sqrt{2}} \Rightarrow B_0=\sqrt{2} B _{rms}$
$B_0=\sqrt{2} \times \frac{E _{rms}}{c}\quad $ From equation (i)
$=\frac{\sqrt{2} \times 6}{3 \times 10^{8}}=2.83 \times 10^{-8} T$
BETA
