. How electromagnetic wave propagate in a medium
The propagation of electromagnetic wave is also due to inertial and elastic properties of the medium. Every medium (including vacuum) has inductive property described by what we call the magnetic permeability of the medium. This property provides the magnetic inertia of the medium. The elasticity of the medium is provided by the capacitive property called the electrical permittivity of the medium. Permeability states the magnetic energy and permittivity stores the electric field energy. This electromagnetic energy propagates in the medium in the form of electromagnetic waves.