Which type of waves require a medium for their propagation?

Mechanical waves are the type of waves that require a medium for their propagation. This means they cannot travel through a vacuum; instead, they depend on the interaction of particles within the medium—such as solids, liquids, or gases—to transmit energy. When a mechanical wave moves through a medium, it causes oscillations of the particles in that medium. A common example of mechanical waves includes sound waves, which travel through air by compressing and rarefying air molecules.

In contrast, electromagnetic waves, such as radio waves and infrared waves, do not require a medium; they can travel through a vacuum. This distinction is critical in understanding wave behavior and propagation. Hence, the identification of mechanical waves as the waves that need a medium aligns well with the fundamental principles of wave physics.