Answer
(a) This situation does not represent an electromagnetic wave.
(b) This situation represents a possible electromagnetic wave.
Work Step by Step
To find the direction of the electromagnetic wave, we can find $E \times B$
To apply the right hand rule to electromagnetic waves, the thumb points in the direction of the electric field, the index finger points in the direction of the magnetic field, and the palm faces toward the direction of the wave's motion.
(a) The thumb points up in the +z direction, and the index finger points to the right in the +y direction. According to the right hand rule, the electromagnetic wave should be traveling in the -x direction.
Since the wave in the diagram is traveling in the +x direction, this situation does not represent an electromagnetic wave.
(b) The thumb points into the page to the right, and the index finger points upward. According to the right hand rule, the electromagnetic wave should be traveling in the direction of the green arrow in the diagram.
Therefore, this situation represents a possible electromagnetic wave.
