# what is the significance of wavenumber. why is it introduced.

Sudheesh Singanamalla
114 Points
13 years ago

What is the physical significance of the wavenumber? For a linear,
isotropic medium, it's an alternative way of expressing the frequency. In
this usage, I'd say that the frequency is the fundamental quantity, but
it's convenient to use the wavenumber, since the wavevector is important.
Due to the temporal boundary conditions, if we have linear media, if we
have frequency w=w1 in one medium, we have w=w1 in all media - there won't
be any conversion of one frequency to another.

For an absorbing medium, the wavenumber tells us how quickly the wave is
absorbed. The frequency doesn't tell us this - this is a practical use for

The wavenumber is the number of wavelengths that fit in a reference
length, e.g., cm^(-1), reciprocal centimeters, kaisers in infrared
spectroscopy.

The only signifance of wavenumber in the absense of a frequency,
is the same as the signifance of the speed of light in the absense
of a frequency, which is standing waves.

Hope that helps