
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 | Mercury | violet | 1 |
g | 435.83 | Mercury | blue | 1 |
F' | 479.99 | Cadmium | blue | 1 |
F | 486.13 | Hydrogen | blue | 1 |
e | 546.07 | Mercury | green | 1 |
d | 587.56 | Helium | yellow | 1 |
632.8 | Neon | red* | 2 | |
C' | 643.85 | Cadmium | red | 1 |
C | 656.27 | Hydrogen | red | 1 |
r | 706.52 | Helium | red | 1 |
* - This is the color emitted by the common He-Ne laser.
References
[1] Kidger [Kidger2002].
[2] Hecht and Zajac [HechtAndZajec1974]