In optics, an optical medium is material through which light and other electromagnetic waves propagate. It is a form of transmission medium. The permittivity and permeability of the medium define how electromagnetic waves propagate in it.

Properties

edit

The optical medium has an intrinsic impedance, given by

 

where   and   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  , where   is the frequency and   is the wavelength of the electromagnetic waves. This equation also may be put in the form

 

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

The propagation velocity of electromagnetic waves in free space, an idealized standard reference state (like absolute zero for temperature), is conventionally denoted by c0:[1]

 
where   is the electric constant and   is the magnetic constant.

For a general introduction, see Serway[2] For a discussion of synthetic media, see Joannopoulus.[3]

Types

edit
  1. Homogeneous medium vs. heterogeneous medium
  2. Transparent medium vs. opaque body

See also

edit

Notes and references

edit
  1. ^ With ISO 31-5, NIST and the BIPM have adopted the notation c0.
  2. ^ Raymond Serway & Jewett J (2003). Physics for scientists and engineers (6th ed.). Belmont CA: Thomson-Brooks/Cole. ISBN 0-534-40842-7.
  3. ^ John D Joannopouluos; Johnson SG; Winn JN; Meade RD (2008). Photonic crystals : molding the flow of light (2nd ed.). Princeton NJ: Princeton University Press. ISBN 978-0-691-12456-8.