What type of waves require a medium to travel through?

Mechanical waves are the correct answer because they require a medium, such as air, water, or solid materials, to propagate. These waves transfer energy through the vibration of particles in the medium. This need for a medium distinguishes them from electromagnetic waves, which can travel through a vacuum and do not require any material substance for propagation.

Mechanical waves can be further classified into two types: longitudinal waves and transverse waves. In longitudinal waves, such as sound waves, the particle displacement occurs in the same direction as the wave travel, while in transverse waves, such as those seen on a string, the particle displacement is perpendicular to the direction of wave travel. However, both types of waves still rely on a medium to carry them, which reinforces why mechanical waves, as a category, answer the question accurately.