Q.

In a double slit experiment the distance between the slits is 0.1 cm and the screen is placed at 50 cm from the slits plane. When one slit is covered with a transparent sheet having thickness t and refractive index n (= 1.5), the central fringe shifts by 0.2 cm. The value of t is __________ cm.   [2026]

1 6.0×10-3  
2 5.6×10-4  
3 8×10-4  
4 8×10-4  

Ans.

(3)

dsinθ=(μ-1)t

d[xD]=(μ-1)t

t=xdD(μ-1)

 =(0.2)(0.1)50(1.5-1)

t=8×10-4 cm