Electromagnetic Waves - Result Question 12
12. The electric field part of an electromagnetic wave in a medium is represented by $E_x=0$;
$E_y=2.5 \frac{N}{C} \cos [(2 \pi \times 10^{6} \frac{rad}{m}) t-(\pi \times 10^{-2} \frac{rad}{s}) x] ;$ $E_z=0$. The wave is :
[2009]
(a) moving along $x$ direction with frequency $10^{6} Hz$ and wave length $100 m$.
(b) moving along $x$ direction with frequency $10^{6} Hz$ and wave length $200 m$. (c) moving along $-x$ direction with frequency $10^{6} Hz$ and wave length $200 m$.
(d) moving along y direction with frequency $2 \pi \times 10^{6} Hz$ and wave length $200 m$.
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Answer:
Correct Answer: 12. (b)
Solution:
- (b) Comparing with the equation of wave. $E_y=E_0 \cos (\omega t-kx)$
$\omega=2 \pi f=2 \pi \times 10^{6} \quad \therefore f=10^{6} Hz$
$\frac{2 \pi}{\lambda}=k=\pi \times 10^{-2} m^{-1}, \lambda=200 m$
