1. Waves Transfer Energy

A wave is a disturbance that transfers energy from place to place. The medium may wiggle, but the energy travels onward. Water waves move energy across the surface while the water mostly moves up and down.

Deep explanation. Waves transfer energy without usually carrying matter from start to finish. In a water wave, a floating object mostly moves up and down as the wave passes; it does not travel across the whole lake with the wave. In sound, air particles vibrate back and forth while the sound energy moves outward.

Some waves need a medium, which is the matter the wave travels through. Sound needs air, water, or another material. Water waves need water. Light is different because it is electromagnetic and can travel through empty space.

How GED® asks it. If a question asks what waves carry, the best answer is energy. If it asks what the medium does, the medium vibrates or is disturbed as the energy passes through.

⚠️ Common misconception: waves carry the material all the way with them. Usually the material vibrates around a resting position while energy moves.

💡 Tip: wave = energy transfer.