[单选题]
The wavelength of a ruby laser is 694.3 nm. What is the energy dibg: f.g1uo-jh ) 4ybpwfference betw( e1cm70.6tnmdm bwsh een the two energy stbdw7 n .c01sem(h6mmt ates involved in laser action?
A. $1.537 \; eV$
B. $1.646 \; eV$
C. $1.786 \; eV$
D. $1.812 \; eV$