Step 1: Understanding the Concept:
Waves propagate in two primary ways: longitudinal (oscillations parallel to the direction of travel) and transverse (oscillations perpendicular to the direction of travel).
Step 2: Key Formula or Approach:
The approach relies on eliminating wave phenomena that apply universally. We must identify a physical phenomenon that is mathematically and physically impossible for oscillations that lack perpendicular components.
Step 3: Detailed Explanation:
Phenomena such as reflection, interference, and diffraction are general wave properties. Both longitudinal waves (like sound) and transverse waves (like light) exhibit these effects. Therefore, they cannot definitively prove whether a wave is transverse or longitudinal.
Polarization is the process of restricting the vibrations of a wave to a single plane.
For a longitudinal wave, oscillations happen only along the single axis of propagation, so there are no multiple planes to restrict. Thus, longitudinal waves cannot be polarized.
Transverse waves have oscillations in the infinite planes perpendicular to the propagation axis. Passing them through a polarizer filters out all but one plane of oscillation.
Because electromagnetic waves can be polarized, it is absolute proof that their electric and magnetic field oscillations are perpendicular to the direction of propagation (transverse).
Step 4: Final Answer:
The correct option is (C).