Question

The electric field associated with an

e. m. wave in vacuum is given by ˆ e i 40 cos (kz – 6 × 108t), where e, z and t are in volt/m, meter and seconds respectively. the value of wave vector k is

Answer 1

Angular speed = 2πf = 6×108 rad/s
or 2πc/λ = 6×108
or kc= 6×108 { Since k=2π/λ}
or k= 6×108/c
{Where c is the speed of light

Answer 2

Answer:

k = 2 m‐¹

Explanation:

w = 6 x 10⁸

2 π f = 6 x 10⁸

2 π f = 6 x 10⁸

2 π c/λ = 6 x 10⁸

2π//λ x c = 6 x 10⁸

k x c = 6 x 10⁸

{ k = 2π//λ = wave factor }

k = 6 x 10⁸/c

k = 6 x 10⁸/c

k = 6 x 10⁸ / 3 x 10⁸

k = 2 m‐¹