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