We know that, when we use quantum wave plate then a linear polarized beam change circular polarized beam.
t1/4 = \(\cfrac14\)= \(\cfrac{\lambda}{(H_0-H_e)}\)
where, H0 = refractive index of ordinary wave
He = refractive index of extra ordinary wave.
H0 - He = \(\cfrac{\lambda}{4t_{t/4}}\)
H0 - He = \(\cfrac{6\times10^{-5}}{4\times0.003}\)
H0 - He = \(\cfrac{6\times10^{-2}}{12}\)
H0 - He = 0.5 x 10-2