distance in the direction of propagation of a periodic wave between two successive positions at which the phase is the same
Note 1 to entry: The wavelength in a medium is equal to the wavelength in vacuo divided by the refractive index of the medium. In photometry, unless otherwise stated, values of wavelength are generally those in air. The refractive index of standard air (for spectroscopy:
Note 3 to entry:
Note 4 to entry: The wavelength is expressed in metres (m) or decimal multiples and submultiples of metre.
Note 5 to entry: In optical radiation the units nanometre (nm) and micrometre (μm) are generally used.
Note 6 to entry: This entry was numbered 845-01-14 in IEC 60050-845:1987.
Note 7 to entry: This entry was numbered 17-1426 in CIE S 017:2011.