Question

Light of wavelength 500nm falls on two narrow slits placed at a distance d = 0.05 mm apart at angle $\varphi ={30}^{\circ }$ relative to the slits shown in figure. On the lower slit a transparent slab of thickness 0.1mm and refractive index 1.5 is placed. The interference pattern is observed on a screen at a distance D = 2m from the slits.

If we remove the transparent slab from the lower slit, the number of fringes that will pass over C is

• A. 50
• B. 10
• C. 100
• D. 500

Answer 1

The correct option is C 100

At C, number of fringes shifted
$n=\frac{(\mu -1)t}{\lambda }=100$