An electromagnetic wave does not require a medium to propagate. It can travel through a vacuum, which is essentially an empty space devoid of matter. This is one of the fundamental properties of electromagnetic waves.
Electromagnetic waves consist of oscillating electric and magnetic fields that are perpendicular to each other and propagate in the form of waves. These waves are generated by the acceleration of charged particles or by changes in electric and magnetic fields.
In a vacuum or empty space, the electric and magnetic fields of an electromagnetic wave can sustain and support each other, allowing the wave to propagate. The changing electric field induces a changing magnetic field, and vice versa, resulting in a self-sustaining wave that can travel indefinitely.
Unlike mechanical waves, such as sound waves or water waves, which require a physical medium like air or water to travel through, electromagnetic waves do not rely on any material substance for their propagation. This is why electromagnetic waves can travel through a vacuum, where no material medium exists.
However, it's important to note that electromagnetic waves can also propagate through different materials, such as air, water, or various solids. When electromagnetic waves pass through a medium, their propagation characteristics can be altered due to interactions with the atoms or molecules of the medium. This leads to phenomena like refraction and absorption, which affect the speed and intensity of the wave.