For a certain electromagnetic wave in free space, at one instant the electric field vector points in the +z direction while the magnetic field vector points in the +x direction, as shown in the figure. In what direction is this wave traveling?
A) +x
B) -x
C) +y
D) -y
E) +z

Question

For a certain electromagnetic wave in free space, at one instant the electric field vector points in the +z direction while the magnetic field vector points in the +x direction, as shown in the figure. In what direction is this wave traveling? 
A) +x 
B) -x 
C) +y 
D) -y 
E) +z

Quizplus · Accepted Answer

According to the right-hand rule, the direction of propagation (i.e. the direction the wave is traveling) is perpendicular to both the electric and magnetic field vectors. In this case, the electric field vector is in the +z direction and the magnetic field vector is in the +x direction. Thus, the direction of propagation must be in the +y direction, which is perpendicular to both the +z and +x directions.

For a Certain Electromagnetic Wave in Free Space, at One