What is intrinsic impedance and Brewster angle?

37. What is intrinsic impedance and Brewster angle?

Intrinsic Impedance:

    Intrinsic impedance, often denoted by the symbol "η" (eta), is a fundamental property of a medium through which an electromagnetic wave propagates. It represents the ratio of the electric field intensity to the magnetic field intensity of the wave in that medium. Intrinsic impedance is also known as characteristic impedance or wave impedance.

Intrinsic impedance and Brewster angle

Mathematically, intrinsic impedance is given by:

η = √(μ / ε)

where:

    η is the intrinsic impedance of the medium (measured in ohms).
    μ (mu) is the permeability of the medium (measured in henries per meter, H/m).
    ε (epsilon) is the permittivity of the medium (measured in farads per meter, F/m).

In free space, which is the vacuum or air, the intrinsic impedance is approximately equal to 377 ohms. In different materials or media, the intrinsic impedance can vary, depending on their permeability and permittivity. The intrinsic impedance plays a crucial role in understanding wave propagation and reflection at the interface between different media, as it influences the behavior of electromagnetic waves as they transition from one medium to another.

    Brewster Angle:

    The Brewster angle, named after the Scottish physicist Sir David Brewster, is an angle of incidence at which a polarized electromagnetic wave undergoing reflection at an interface experiences no parallel polarization (p-polarization) reflection. In other words, at the Brewster angle, the reflected wave has purely perpendicular polarization (s-polarization).

For an electromagnetic wave incident on a dielectric interface (e.g., between air and glass), the Brewster angle (denoted by "θ_B") is given by the following equation:

tan(θ_B) = n2 / n1

where:

    θ_B is the Brewster angle.
    n1 is the refractive index of the first medium (incident medium).
    n2 is the refractive index of the second medium (transmitted medium).

The Brewster angle has practical applications in optics and engineering. For instance, it can be used to reduce glare on glass surfaces, such as windows or camera lenses, by positioning the surfaces at the Brewster angle with respect to incident light. Additionally, it is relevant in the design of optical coatings and polarizing filters for various optical devices.