Eduprobe
Question:
In Young's double slit experiment, the distance between slits and the screen is 1.0m and monochromatic light of 600nm is being used. A person standing near the slits is looking at the fringe pattern. When the separation between the slits is varied, the interference pattern disappears for a particular distance d0 between the slits. If the angular resolution of the eye is 1°/60, the value of d0 is close to:
3mm
4mm
1mm
2mm
Solution:
Fringe Width = β=Lλ/d
Angle subtended on eye = β
L/d = λ/d ⇒ θ = λ/d = 1°/60 Degree
⇒ θ = λ/d = 1/60 × 2π/360 radians
⇒ d = λ × 2/16002π = 600 × 10⁻⁹ × 2/16002π = 2063700 × 10⁻⁹ = 2 × 10⁻³ = 2mm