Bright Fringe Condition for Young's Double - Slit Interference

Formula: Δ L = d (x)/(D) = kλ, where Δ L is the optical path difference, d is the slit separation, D is the distance from slits to screen, x is the distance on the screen from the central axis, k is the interference order ( k = 0, ±1, ±2,... ), and λ is the wavelength of light. Applicable Conditions: Monochromatic light source, parallel and equally wide slits, slit width much smaller than the wavelength, observation screen distance much larger than the slit separation. Explanation: When this condition is met, a bright fringe (constructive interference) appears at the corresponding position on the screen.