Optical medium

An optical medium is material through which electromagnetic waves propagate. It is a form of transmission medium. The permittivity and permeability of the medium define how electromagnetic waves propagate in it. The medium has an intrinsic impedance, given by

where E x and H y are the electric field and magnetic field, respectively. In a region with no electrical conductivity, the expression simplifies to:

For example, in free space the intrinsic impedance is called the characteristic impedance of vacuum, denoted Z₀, and

Waves propagate through a medium with velocity c w = ν λ , where ν is the frequency and λ is the wavelength of the electromagnetic waves. This equation also may be put in the form

where ω is the angular frequency of the wave and k is the wavenumber of the wave. In electrical engineering, the symbol β , called the phase constant, is often used instead of k .

The propagation velocity of electromagnetic waves in free space, an idealized standard reference state (like absolute zero for temperature), is conventionally denoted by c₀:

For a general introduction, see Serway For a discussion of man-made media, see Joannopoulus. Types of optical mediums

1 Homogenous medium 2 Heterogeneous medium 3 Transparent medium 4 Translucent medium 5 Opaque body