In Young's double slit experiment a light of wavelength λ is used. When screen is shifted by 5×10−2m towards the slits the change in fringe width is 10−3m. Find the value of λ if distance between slits is 3×10−5m.

fringe width. β=λDdWhere λ is the wavelength of light, D is the distance between screen and the slits and d is the distance between two slits ∴Δβ=ΔD or λ=ΔβdΔD( As λ and d are constant)Substituting the given values, we getλ=3×10−7m10−3m5×10−2m=6×10−7m=6000Å