Question

Choose the correct answer from the alternatives given. The electric field part of an electromagnetic wave in a medium is represented $E_x=0,$ $E_y=2.5\frac{N}{C}cos[(2\pi \times {10}^6\frac{rad}{m})t-(\pi \times {10}^{-2}\frac{rad}{s})x],E_z=0.$ The wave is

• A. moving along x direction with frequency ${10}^6$Hz and wavelength 100 m
• B. moving along x direction with frequency ${10}^6$Hz and wavelength 200 m
• C. moving along -x direction with frequency ${10}^6$ Hz and wavelength 200 m
• D. moving along y direction with frequency $2\pi \times {10}^6$ Hz and wavelength 200 m

Answer 1

The correct option is B moving along x direction with frequency ${10}^6$Hz and wavelength 200 m

$E_y=2.5\frac{N}{C}\times cos[(2\pi \times {10}^6\frac{rad}{m})t-(\pi \times {10}^{-2}\frac{rad}{s}x)]$

$E_z=0,E_x=0$

The wave is moving in the positive direction of x. This is in the form $E_y=E_{0}cos(\omega t-kx)$

$\omega =2\pi \times {10}^6$

$2\pi \upsilon =2\pi \times {10}^6\Rightarrow \upsilon ={10}^{6}Hz$

$\frac{2\pi }{\lambda }=k\Rightarrow \frac{2\pi }{\lambda }=\pi \times {10}^{-2}or\lambda =200m$