When an electromagnetic (EM) wave undergoes reflection, its polarization can change depending on the angle of incidence and the properties of the reflecting surface.
Polarization refers to the orientation of the electric field vector of an EM wave. It can be categorized into different types: linear polarization, circular polarization, and elliptical polarization. For simplicity, let's focus on linear polarization, where the electric field oscillates in a specific direction.
When a linearly polarized EM wave is incident on a smooth and flat surface at an angle, the reflected wave will generally retain its original polarization if the incident wave is perpendicular (or parallel) to the plane of incidence. This is known as specular reflection.
However, if the incident wave is inclined at an angle with respect to the plane of incidence, the reflected wave will have a different polarization. Specifically, the polarization of the reflected wave will be perpendicular to the plane of incidence. This phenomenon is known as Brewster's angle. At this particular angle of incidence, the reflected wave becomes completely polarized with its electric field perpendicular to the plane of incidence.
For example, if the incident wave is linearly polarized in the vertical direction (perpendicular to the plane of incidence), the reflected wave will be linearly polarized in the horizontal direction (parallel to the plane of incidence) at Brewster's angle.
It's important to note that the polarization change upon reflection only occurs for waves incident on a dielectric surface at an angle other than perpendicular or parallel to the surface. The exact change in polarization depends on the angle of incidence and the specific characteristics of the reflecting surface, such as its refractive index.
In summary, when an EM wave undergoes reflection, its polarization may change depending on the angle of incidence. Specular reflection retains the original polarization, while at Brewster's angle, the reflected wave becomes completely polarized perpendicular to the plane of incidence.