An electromagnetic wave is propagating towards the west in free space. At a certain moment the direction of the magnetic field vector associated with this wave points vertically upward.
What is the direction of the electric field vector?

A. vertical and pointing down.
B. vertical and pointing up.
C. horizontal and pointing north.
D. horizontal and pointing south.
E. horizontal and pointing east.

The direction of the electric field vector is horizontal and pointing north.

Option (C) is correct option.

Explanation:

Given :

The direction of wave propagation is toward the west.

The direction of magnetic field vector is vertically upward.

According to the theory of electromagnetic wave propagation, the electric field and magnetic field is perpendicular to each other and the direction of propagation is also perpendicular to both electric and magnetic field vector.

⇒  

From right hand rule, the fingers goes towards horizontal and pointing north and curl the finger goes towards  vertically upward and thumb will give you the direction of wave propagation toward west.

Hence, the direction of electric field vector is horizontal and pointing north.