Which type of wave requires a medium to travel?

Mechanical waves are defined by their requirement for a medium—such as air, water, or solids—to propagate. This means they cannot travel through a vacuum, as they rely on the particles of the medium to transfer energy through vibrations. For instance, sound waves, which are a type of mechanical wave, need air or another medium to carry the sound from one place to another.

In contrast, electromagnetic waves, such as light, radio waves, and microwaves, do not require a medium for their propagation and can travel through a vacuum. This fundamental difference distinguishes mechanical waves from electromagnetic waves, confirming that the correct choice is mechanical waves as the type that necessitates a medium for travel.