Distinguishing transverse and longitudinal waves

Steps:

• Recall that longitudinal waves have oscillations parallel to the direction of energy transfer, like sound waves.
• Recall that transverse waves have oscillations perpendicular to the direction of energy transfer, like electromagnetic waves.
• Identify examples: sound is longitudinal; gamma-rays, ultraviolet, and x-rays are all electromagnetic, so transverse.
• Match options to these definitions to find the correct description.

Why D is correct:

• X-rays are electromagnetic waves, which are transverse by definition, meaning particle oscillations occur perpendicular to the propagation direction.

Why the others are wrong:

• A: Gamma-rays are electromagnetic (transverse), so oscillations are perpendicular, not parallel.
• B: Ultraviolet waves are electromagnetic (transverse), so oscillations are perpendicular, not parallel.
• C: Sound waves are longitudinal, so oscillations are parallel, not perpendicular.

Final answer: D