Q.

In a Young double slit experiment, the wavelength of incident light is 6000 Å, the separation between slits S1 and S2 is 5 cm and the distance between slits plane and screen is 50 cm, as shown in the figure below. If the resultant intensity at P is equal to the intensity due to individual slits, the path difference between interfering waves is ______ Å.       [2026]

1 4000  
2 3000  
3 2000  
4 1000  

Ans.

(3)

Ip=I0=4I0cos2Δϕ2

cosΔϕ2=12⇒Δϕ=2π3

2πλΔx=Δϕ=2π3

Δx=λ3=2000 Å