Q.

In a Young's double slit experiment, a combination of two glass wedges A and B, having refractive indices 1.7 and 1.5, respectively, are placed in front of the slits, as shown in the figure. The separation between the slits is d = 2 mm and the shortest distance between the slits and the screen is D = 2 m. Thickness of the combination of the wedges is t=12 μm. The value of l as shown in the figure is 1 mm. Neglect any refraction effect at the slanted interface of the wedges. Due to the combination of the wedges, the central maximum shifts (in mm) with respect to O by ________.                  [2025]


Ans.

(1.2)

From figure, x+y=12 μm

412=1x     ∴  x=3 μm,   y=9 μm

∴  Δ=-ydD-(μB-1)x-(μA-1)y+(μB-1)y+(μA-1)x

-ydD=-0.5×3-0.7×9+0.5×9+0.7×3

-ydD=-0.5×6-0.7×6⇒-ydD=-1.2 μm

⇒y=1.2×Dd×10-6

=1.2×22×10-3×10-6

=1.2 mm