surfaces (in mid air) of constant OPL (optical path length)
In a perfect optical system or a first order optical system all wavefronts are either planar or spherical.
Wavefronts stay after reflection perpendicular to the propagation direction of the light.
number of wavelengths per cm
[table caption=”sample wavenumbers” width=”300″ colwidth=”100|100|100″ colalign=”left|left|left”]
wavenumber (cm^-1),wavelength (um),frequency (THz)
22727,0.440,682
18181,0.550,545
15152,0.660,455
11765,850,353
10000,1,300
1000,10,30
[/table]