When an electromagnetic wave encounters an interface between two different media (such as air and glass or air and water), three key phenomena can occur: reflection, refraction, and transmission. The wave’s behavior at the interface is determined by the properties of the media, such as their permittivity, permeability, and conductivity.
- Reflection: Reflection occurs when a portion of the incident electromagnetic wave is redirected back into the medium from which it originated. The angle of incidence (the angle between the incident wave and the surface normal) is equal to the angle of reflection (the angle between the reflected wave and the surface normal). Reflection is affected by the properties of the materials, the angle of incidence, and the polarization of the wave. When the interface between the media is a good conductor, most of the incident energy is reflected back.
- Refraction: Refraction is the change in direction of an electromagnetic wave as it passes from one medium to another, due to the difference in the speed of light in the two media. This causes the wave to bend at the interface, following Snell’s law:
n1 * sin(θ1) = n2 * sin(θ2)
where n1 and n2 are the refractive indices of the first and second media, and θ1 and θ2 are the angles of incidence and refraction, respectively. The refractive index (n) is related to the medium’s permittivity (ε) and permeability (μ) as follows:
n = √(ε * μ)
- Transmission: Transmission occurs when a portion of the incident electromagnetic wave passes through the interface and continues to propagate in the second medium. The amount of energy transmitted depends on the properties of the media, the angle of incidence, and the polarization of the wave. In some cases, such as when the angle of incidence exceeds the critical angle for total internal reflection, no transmission occurs, and all the incident energy is reflected back into the first medium.
The fractions of the incident electromagnetic wave’s energy that are reflected, refracted, and transmitted depend on the media’s properties and the wave’s angle of incidence and polarization. In many applications, such as fiber optics, radar, and wireless communication, understanding these phenomena is crucial for the design and optimization of systems that interact with electromagnetic waves.