Vd = (nd-1)/(nF-nC)
d: 0.58756 µm (Yellow helium line)
F: 0.48613 µm (Blue hydrogen line)
C: 0.65627 µm (Red hydrogen line)

Ve = (ne-1)/(nF'-nC')
e: 0.54607 µm (Green mercury line)
F': 0.47999 µm (Blue cadmium line)
C': 0.64385 µm (Red cadmium line)