Medium (optics)

\eta = \sqrt{\mu \over arepsilon}

where

\mu

is the ''permeability'' of the medium and

arepsilon

is the ''permittivity'' of the medium.

Waves propagate through a medium with velocity

c_w = 
u \lambda

, where

u

is the Frequency and

\lambda

is the Wavelength of the electromagnetic waves. This can also be put in the form
:

c_w = {\omega \over k}\ ,

where

\omega

is the Angular Frequency of the wave and

k

is the Wavenumber of the wave. In Electrical Engineering , the symbol

\beta

, called the ''phase constant'', is often used instead of

k

.

The propagation velocity of electromagnetic waves in free space, i.e. the absence of a medium, is
:

c_w = {1 \over \sqrt{arepsilon_0 \mu_0}}\ ,

:where

arepsilon_0

is the permittivity of free space
::

~ \mu_0 ~

is the permeability of free space.

SEE ALSO

REFERENCES

Information About