Final answer:
A plane electromagnetic wave has perpendicular electric and magnetic fields. The magnetic field can be calculated from the electric field using the speed of light, B = E/c. The direction of the magnetic field follows the right-hand rule relative to the electric field and wave travel.
Step-by-step explanation:
Understanding Electromagnetic Waves
A plane electromagnetic wave consists of oscillating electric and magnetic fields that are perpendicular to each other and the direction of the wave's propagation. Considering a wave traveling in a vacuum, the electric field (E) and magnetic field (B) are related by the speed of light (c), such that B = E/c, where c is approximately 3 x 10^8 m/s in vacuum.
To determine the magnetic field at a given instant when the electric field is known, we can use this relationship. For example, if an electric field of a plane electromagnetic wave is given as 6.0 V/m, the corresponding magnetic field would be 2 x 10^-8 T, considering the electric field direction is perpendicular to the magnetic field and the direction of wave travel, following the right-hand rule. The magnetic field's direction will be such that it follows this rule relative to the given electric field and the positive direction of wave propagation.