Physics Concept: Electromagnetic Waves
Question:
Which of the following statements properly describes electromagnetic (EM) waves?
- A. They are longitudinal waves with mutually perpendicular electric and magnetic field vectors.
- B. They are transverse waves with mutually perpendicular electric and magnetic field vectors.
- C. They are longitudinal waves with parallel electric and magnetic field vectors.
- D. They are transverse waves with parallel electric and magnetic field vectors.
Answer:
Correct Option: B
- The electric field (E) oscillates in one direction.
- The magnetic field (B) oscillates in a direction perpendicular to the electric field.
- Both E and B fields are also perpendicular to the direction of wave propagation.
This orthogonal arrangement forms a three-dimensional configuration where the electromagnetic wave moves forward, with the electric and magnetic fields continuously regenerating each other in perpendicular planes.
The direction of the wave’s propagation is determined by the vector cross product of the electric and magnetic field vectors: Direction = E × B.
Since EM waves do not require a medium to propagate and involve perpendicular oscillations of fields, they cannot be longitudinal. Longitudinal waves, like sound, have vibrations along the direction of travel, which does not apply here.
Conclusion:
The statement that properly describes electromagnetic waves is:
“They are transverse waves with mutually perpendicular electric and magnetic field vectors.”