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 µm, then distance by which these fringes will be shifted will be

2 mm

$\frac{x d}{D}(\mu-1) t \Rightarrow x=\frac{(\mu-1) t D}{d}$

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