In Young's double slit experiment, two slits S1 and S2 are 'd' distance apart and the separation from slits to screen is D (as shown in figure). Now if two transparent slabs of equal thickness 0.1 mm but refractive index 1.51 and 1.55 are introduced in the path of beam (λ=4000 Å) from S1 and S2 respectively. The central bright fringe spot will shift by ______ number of fringes.
Answer: 10
Solution
The two slabs add an extra optical path at the centre equal to (μ2−μ1)t=(1.55−1.51)(0.1mm)=4×10−6m. The number of fringes through which the central maximum shifts is this path difference divided by the wavelength, λ(μ2−μ1)t=4000×10−104×10−6=10. The central bright fringe shifts by 10 fringes.
JEE Main · 2023 · 30 Jan 2023 · Shift 1 · Integer answer
