The electric field part of an electromagnetic wave in a medium is represented by Ex = 0; Ey = 2.5N/Ccos [(2π× 10⁶rad/s)t - (π× 10⁻²rad/m)x]; Ez = 0. The wave is (a) moving along x direction with frequency 106 Hz and wavelength 100 m. (b) moving along x direction with frequency 106 Hz and wavelength 200 m. (c) moving along - x direction with frequency 106 Hz and wavelength 200 m. (d) moving along y direction with frequency 2π× 10⁶ Hz and wavelength 200 m.

Answer: (b). ω = 2π×10⁶ ⇒ f = 10⁶ Hz. k = π×10⁻² ⇒ λ = 2π/k = 200 m. Phase (ω t - kx) means travel along +x. So the answer is (b) along x, 10⁶ Hz, 200 m.

The electric field part of an electromagnetic wave in a medium is… | NEET 2009 (AIPMT)

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Nature of EM Waves & Wave Equation

The electric field part of an electromagnetic wave in a medium is represented by Ex = 0; $E_y = 2.5\frac{\text{N}}{\text{C}}\cos\left[\left(2\pi\times 10^{6}\frac{\text{rad}}{\text{s}}\right)t - \left(\pi\times 10^{-2}\frac{\text{rad}}{\text{m}}\right)x\right];$

Ez = 0. The wave is

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Answer: (b)

$\omega = 2\pi\times10^{6} \Rightarrow f = 10^{6}$ Hz.
$k = \pi\times10^{-2} \Rightarrow \lambda = \dfrac{2\pi}{k} = 200$ m.
Phase $(\omega t - kx)$ means travel along $+x$ .
So the answer is (b) along x, $10^{6}$ Hz, 200 m.

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