A transverse wave can be distinguished from a longitudinal wave by

1. Analyze the question You are asked which wave property can tell a transverse wave apart from a longitudinal wave. That means a property that only one of the two types shows.

2. Explain the concept

• In a transverse wave, particles vibrate perpendicular to the direction the wave travels (e.g. light waves, waves on a rope, water ripples).
• In a longitudinal wave, particles vibrate parallel to the direction of travel (e.g. sound waves, compressions and rarefactions in a spring).

Because a transverse wave vibrates in more than one possible plane perpendicular to its direction of travel, we can restrict the vibration to a single plane. This is called polarization. A longitudinal wave vibrates only along its direction of travel, so there is no perpendicular plane to restrict, and it cannot be polarized.

3. Solution: test each option

• A. Diffraction: both transverse and longitudinal waves bend around obstacles, so it cannot distinguish them.
• B. Reflection: both types reflect (sound echoes, light mirrors), so it cannot distinguish them.
• C. Refraction: both types change speed and direction when they enter a new medium (sound and light both refract), so it cannot distinguish them.
• D. Polarization: only transverse waves can be polarized, so this is the distinguishing property.

4. Answer The correct option is D. Polarization.

5. Exam tip Remember: "Polarization = Perpendicular." Only transverse waves, which vibrate perpendicular to the direction of travel, can be polarized. Reflection, refraction, diffraction and interference are common to all waves, so they never separate the two types.