Given that, equation of electric field of an electromagnetic wave in vacuum, E=(3.1NC−1) cos[(1.8‌rad‌‌‌m−1)y+(54×106‌rad‌‌‌s−1)1]‌
^
i
...(i) We know that, general equation E=E0‌cos[ky+wt]‌
^
i
...(ii) Comparing Eqs. (i) and (ii), we getPropagation constant, k=1.8‌rad∕m i.e.,
2Ï€
λ
=1.8 ⇒λ=
2Ï€
1.8
=3.49m Hence, wavelength of electromagnetic wave is 3.49m.