Practice question

Given: What is the distance of the fifth dark fringe from the ntral maximum in a double-slit experiment if lambda = 650 nm, d = 0.5 mm, and D = 1.0 m ? Formula: Dark fringe position x_n = frac(n + 1/2) lambda Dd. Substitution & Calculation: For the fifth dark fringe, n = 4 . lambda = 6.5 × 10⁻⁷m, d = 5.0 × 10⁻⁴m, D = 1.0 m . x_4 = frac(4 + 1/2) × 6.5 × 10⁻⁷ × 1.05.0 × 10⁻⁴= frac4.5 × 6.5 × 10⁻⁷⁵.0 × 10⁻⁴= 5.85 × 10⁻³m = 5.85 mm . Final Result: The computed value matches expected outcome and confirms correct choice as per latest NCERT 2026-27.