Question

Name the phenomenon that proves the transverse nature of light.

• A. Diffraction
• B. Interference
• C. Polarisation
• D. Reflection

Hint:

Polarisation is the key experimental evidence that light waves are transverse. Other wave phenomena such as interference and diffraction occur in both transverse and longitudinal waves, but polarisation occurs only in transverse waves.

Answer 1

The Correct Option is C

Concept:
Light waves are electromagnetic waves. Wave motion can be either longitudinal (oscillations parallel to travel) or transverse (oscillations perpendicular to travel).
Step 1: Understanding the Question:
We need to identify which optical phenomenon can \textit{only} occur if the wave is transverse.
Step 2: Key Formula or Approach:
Analyze different wave behaviors:
- Reflection/Refraction: Common to all waves.
- Interference/Diffraction: Common to both longitudinal (sound) and transverse waves.
- Polarisation: Possible only when oscillations occur in a plane perpendicular to the direction of propagation.
Step 3: Detailed Solution:
1. Polarisation involves restricting the vibrations of a wave to a single plane.
2. In a longitudinal wave (like sound), vibrations are back and forth along the direction of travel; there is no "side-to-side" oscillation to restrict.
3. Only transverse waves have vibrations that can be "filtered" by a polaroid.
4. Since light can be polarised, it must be a transverse wave.
Step 4: Final Answer:
The phenomenon of Polarisation proves the transverse nature of light.