The propagation of electromagnetic radiation, such as light, through a vacuum does not require a medium because it is not a mechanical wave that relies on the oscillation of particles in a medium. Instead, electromagnetic radiation is a combination of electric and magnetic fields that can self-propagate through space.
According to classical electromagnetism, electromagnetic waves are produced by oscillating electric charges. These oscillating charges generate changing electric and magnetic fields that propagate through space. The fields themselves carry the energy and information of the wave. When an electric field changes, it induces a magnetic field, and when a magnetic field changes, it induces an electric field. This interplay of changing electric and magnetic fields perpetuates the wave's propagation.
The nature of electromagnetic radiation is fundamentally different from the movement of particles like atoms or molecules in a medium. Instead of particles, electromagnetic radiation consists of packets of energy called photons. Photons are considered elementary particles and are the quanta of electromagnetic radiation. They do not have a mass or a definite position like classical particles do. Photons exhibit both wave-like and particle-like properties, known as wave-particle duality. This duality is a fundamental aspect of quantum mechanics.
Regarding the "energy" associated with electromagnetic radiation, it refers to the energy carried by the photons themselves. The energy of a photon is directly proportional to its frequency. In the case of light, the different colors or wavelengths correspond to different frequencies and energy levels of the photons. When electromagnetic radiation interacts with matter, it can transfer energy to particles, causing various effects depending on the interaction.
In summary, electromagnetic radiation can propagate through a vacuum because it is composed of electric and magnetic fields that generate and sustain each other as they move through space. While the particles of electromagnetic radiation, called photons, do carry energy, they are fundamentally different from classical particles and exhibit wave-particle duality.