A plane electromagnetic wave travels in vacuum along z-direction. What can you say about the direction of electric and magnetic field vectors?

Explanation

To solve the problem regarding the direction of electric and magnetic field vectors in a plane electromagnetic wave traveling in the vacuum along the z-direction, we can follow these steps:

### Step 1: Identify the Direction of Wave Propagation
The problem states that the electromagnetic wave is traveling along the z-direction. This means that the wave vector \( \vec{k} \) is directed along the z-axis.

### Step 2: Understand the Relationship Between Electric and Magnetic Fields
In an electromagnetic wave, the electric field vector \( \vec{E} \) and the magnetic field vector \( \vec{B} \) are always perpendicular to each other and also perpendicular to the direction of wave propagation. This can be expressed mathematically as:
\[
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