In YDSE with `d = 1 mm` and `D = 1 m`, Slabs of `(t = 1 mu m, mu = 3)` and `(t = 0.5mu m, mu = 2)` are introduced in front of upper and lower slits, respectively. Find the shift in the fringe pattern.

Explanation

Optical path for light coming from upper slit `S_(1)` is
`S_(1)P+1 mu m(2-1)= S_(2)P+0.5 m`
Similarly optical path for light coming from `S_(2)` is
`S_(2)P+0.5mu m(2-1)=S_(2)P+0.5 mu m`
Path difference :
`Delta p = (S_(2)P+0.5 mu m)-(S_(1)P+2mu m)`
`=(S_(2)P-S_(1)P)-1.5 mu m`
`=(yd)/(D)-1.5 mu m`
For central bright fringe `Delta p = 0`
`rArr y = (1.5 mu m)/(1mm)xx 1m = 1.5 mm`.
The whole pattern is shifted by 1.5 mm upwards