Question

What do you understand by terms Is optical medium always a material body eaxplain ?

Answer 1

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

{\displaystyle \eta ={E_{x} \over H_{y}}}

where {\displaystyle E_{x}} and {\displaystyle H_{y}} are the electric field and magnetic field, respectively. In a region with no electrical conductivity, the expression simplifies to:

{\displaystyle \eta ={\sqrt {\mu \over \varepsilon }}\ .}

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

{\displaystyle Z_{0}={\sqrt {\mu _{0} \over \varepsilon _{0}}}\ .}

Waves propagate through a medium with velocity {\displaystyle c_{w}=\nu \lambda }, where {\displaystyle \nu } is the frequency and {\displaystyle \lambda } is the wavelength of the electromagnetic waves. This equation also may be put in the form

{\displaystyle c_{w}={\omega \over k}\ ,}

where {\displaystyle \omega } is the angular frequency of the wave and {\displaystyle k} is the wavenumber of the wave. In electrical engineering, the symbol {\displaystyle \beta }, called the phase constant, is often used instead of {\displaystyle k}.

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

{\displaystyle c_{0}={1 \over {\sqrt {\varepsilon _{0}\mu _{0}}}}\ ,}where {\displaystyle \varepsilon _{0}} is the electric constant and {\displaystyle ~\mu _{0}\ } is the magnetic constant.

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

Types of optical mediums[edit]Homogeneous mediumHeterogeneous mediumTransparent mediumTranslucent mediumOpaque body