The electric field for an electromagnetic wave in free space is E=i 30 cos(kz−5×10⁸t), where magnitude of E is in V/m. The magnitude of wave vector, k is:
(velocity of em wave in free space =3×10⁸m/s)
A. 0.46 rad m⁻¹
B. 3 rad m⁻¹
C. 1.66 rad m⁻¹
D. 0.83 rad m⁻¹