Answer:
Magnetic field, B =
(eastwards)
Step-by-step explanation:
Given that,
The magnitude of electric field, E = 3.7 V/m
A plane electromagnetic wave travels northward. We need to find the magnitude and direction of the magnetic field at this instant.
The relation between the magnetic field and the electric field of the plane electromagnetic wave is given by :

c is the speed of light

So, the magnetic field is
. The direction of magnetic field is perpendicular to the electric field and the direction of wave propagation. Hence, the direction of magnetic field is eastward.