[单选题]
The wavelength of a ruby laser is 694.3 nmz-;q 4 4ncx8 ygmxj/(pk ep.yr. What is the en;4stafu te8*rergy difference between the two energy states involved in laser action?4t*a s8 refut;
A. $1.537 \; eV$
B. $1.646 \; eV$
C. $1.786 \; eV$
D. $1.812 \; eV$