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Atomic lines

The refractive index of optical glass is traditionally measured at the well-defined wavelengths corresponding to optical transitions in an atomic vapor. The traditional wavelengths used to evaluate a visual system are F, d, and C.

Designation Wavelength (nm) Element color Ref.
h 404.65 Mercuryviolet 1
g 435.83 Mercuryblue 1
F' 479.99 Cadmiumblue 1
F 486.13 Hydrogenblue 1
e 546.07 Mercurygreen 1
d 587.56 Heliumyellow 1
632.8 Neonred* 2
C' 643.85 Cadmiumred 1
C 656.27 Hydrogenred 1
r 706.52 Heliumred 1

* - This is the color emitted by the common He-Ne laser.

References

[1] Kidger [Kidger2002].
[2] Hecht and Zajac [HechtAndZajec1974]

See also