The electric field associted with an electromagnetic wave in vacuum is given by `vecE=40 cos(kz-6xx10^(8)t)hati`, when `E`, `z` and `t` are in volt/m metre and second respectively
find the wave vector.

Options

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

Answer

a

Explanation

Here, `E=40cos (kz-6xx10^8t)`
Comparing it with the relation
`E=E_0 cos .(2pi)/lambda(z-vt)=E_0cos ((2pi)/lambdaz-(2pi)/lambdavt)`
we have `(2pi)/lambda=k`
and `(2piv)/lambda=6xx10^8s^-1 or kv=6xx10^8`
or `k=(6xx10^8)/v=(6xx10^8 s^-1)/(3xx10^8ms^-1)=2m^-1`