The electric field associated with an electromagnetic wave in vacuum is given by `vecE=40cos(kz-6xx10^(8)t)hati,`
where E, z and t are in volt per meter, meter and second respectively. The value of wave vector k is

Options

A. `3 m^(-1)`
B. `2 m^(-1)`
C. `0.5 m^(-1)`
D. `6 m^(-1)`

Answer

B

Explanation

comparing given equation with the the general equation we get ,` vecE = E_0 cos ( kx - omega t) hati`
` omega = 6 xx 10^8` rad /s
` = > 2 pi f = 6 xx 10^8 `
` f lamda = c= 3 xx 10 ^8 `
`=( 6xx 10^8 ) /( 2 pi ) lamda = 3 xx 10 ^8 m//s `
`implies lamda = pi m `
wave vector is ` k= ( 2 pi )/( lamda) = ( 2pi) / (pi )= 2.0 m^(-1)`