At a certain point and a certain time the electric field of an electromagnetic wave is in the negative z direction and the magnetic field is in the positive y direction. Which of the following statements is true?
A) Energy is being transported in the positive x direction but half a cycle later, when the electric field is in the opposite direction, it will be transported in the negative x direction
B) Energy is being transported in the positive x direction and half a cycle later, when the electric field is in the opposite direction, it will still be transported in the positive x direction
C) Energy is being transported in the negative x direction but half a cycle later, when the electric field is in the opposite direction, it will be transported in the positive x direction
D) Energy is being transported in the negative x direction and half a cycle later, when the electric field is in the opposite direction, it will still be transported in the negative x direction.
E) None of the above are true.

Question

Quizplus · Accepted Answer

The direction of energy transport for an electromagnetic wave is given by the cross product of the electric and magnetic fields. In this case, the cross product would be in the positive x direction, indicating that energy is being transported in the positive x direction. This direction does not change when the electric field changes direction half a cycle later.

At a Certain Point and a Certain Time the Electric