The electric field associated with an e.m. wave in vacuum is given by

The Electric Field Associated With An Em Wave In Vacuum Physics QuestionThe Electric Field Associated With An Em Wave In Vacuum Physics Question

The electric field associated with an e.m. wave in vacuum is given by E = i 40 cos (kz – 6 x 10⁸ t), where E, z and t are in volt/m, meter and seconds respectively. The value of wave vector k is:

Options

(a) 2 m⁻¹
(b) 0.5 m⁻¹
(c) 6 m⁻¹
(d) 3 m⁻¹

Correct Answer:

2 m⁻¹

Explanation:

On comparing the given equation to
E = a₀i cos (ωt – kz) ω = 6 x 10⁸ ,
k = 2π / r = ω / c
k = ω / c = 6 x 10⁸ / 3 x 10⁸ = 2 m⁻¹

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