Question
The electric field associated with an em wave in vacuum is given by
E = $\widehat i$ 40 cos (kz $-$ 6 $ \times $ 108 t) where E, z and t are in volt/m, meter and seconds respectively. The value of wave vector k is
E = $\widehat i$ 40 cos (kz $-$ 6 $ \times $ 108 t) where E, z and t are in volt/m, meter and seconds respectively. The value of wave vector k is