# Wavelength of sodium light

why sodium has two lines D1 and D2 ?

it may be due to transition between s1/2 and p3/2, p1/2 and p3/2 states

Those are transitions from two fine levels.
That's $$^2P_{1/2} \to ^2S$$ and $$^2P_{3/2} \to ^2S$$

Redbelly98
Staff Emeritus