General Condition for Destructive Interference (Dark Fringe)

Formula: Δ L = (k + (1)/(2))λ, where Δ L is the optical path difference, k is the interference order ( k = 0, ±1, ±2,... ), and λ is the wavelength in vacuum. Applicable Conditions: Superposition of two coherent light beams, without considering additional half - wave loss or having already included it in the optical path difference. Explanation: When the optical path difference between the two beams is an odd multiple of half the wavelength, they are out of phase, resulting in destructive interference and forming a dark fringe.