A plane monochromatic light falls normally on a diaphragm with two narrow slits separated by a distance d = 2.5 mm. A fringe pattern is formed on the screen placed at D = 100 cm behind the diaphragm. If one of the slits is covered by a glass plate of thickness 10  m, then distance by which these fringes will be shifted will be

2 mm

$\frac{xd}{D}(μ-1)t⇒x=\frac{(μ-1)tD}{d}$

or $x=\frac{(1.5-1)×10^{-3}×100}{0.25}=0.2cm=2mm$