Two light waves of wavelengths 800 nm and 600 nm are used in Young's double slit experiment to obtain interference fringes on a screen 7 m away. If slit separation is 0.35 mm, the shortest distance from central bright maximum where bright fringes of the two wavelengths coincide is ______ mm.
Physics · Circular Motion
JEE Mains 31 January 2023 Shift 2 Evening Shift

Question

Two light waves of wavelengths 800 nm and 600 nm are used in Young's double slit experiment to obtain interference fringes on a screen 7 m away. If slit separation is 0.35 mm, the shortest distance from central bright maximum where bright fringes of the two wavelengths coincide is ______ mm.

Physics · Circular Motion

JEE Mains 31 January 2023 Shift 2 Evening Shift

G1 Physics · Accepted Answer

Coincidence requires m₁λ₁ = m₂λ₂. Smallest integers satisfy 3×800 = 4×600 = 2400 nm. Distance y = (mλ)D/d = (2400×10⁻⁹)(7)/(0.35×10⁻³) = 0.048 m = 48 mm.