STANDARDPhysics-Electromagnetic Waves
STANDARD Physics Wave Propagation MCQ Question
Type: MCQ-conceptual-Medium-Class 12
The electric field part of an electromagnetic wave in a medium is represented by Eₓ = 0, Eᵧ = -2.5 N/C cos [(2π × 10⁶ rad/m) t - (π × 10² rad/s) x], E_z = 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
Correct Answer
Option B
Detailed Explanation
Eᵧ = 0, E₁ = 0. The wave is moving in the positive direction of x. This is in the form Eᵧ = E₀ cos (ωt - kx) = 2π × 10⁶ = 2πν ⇒ ν = 10⁶ Hz. Therefore, λ = 2π/k = 2π/π × 10² = 200 m.
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