• Young’s double-slit experiment uses two coherent sources of light placed at a small distance apart, usually, only a few orders of magnitude greater than the wavelength of light is used.
• Young’s double-slit experiment helped in understanding the wave theory of light which is explained with the help of a diagram.
• A screen or photo detector is placed at a large distance ’D’ away from the slits as shown
• S1 & S2 are two coherent sources. GG – screen at a distance D from the sources.
• Let d = distance between the slits (two sources). P = a point at a distance from the middle of the screen where a bright fringe is formed.
• For constructive interference path difference = nλ (S2P) – (S1P) = nλ where n = 0, 1, 2, 3……. From the
Where n = 0, +1, ±2, ± 3 for bright fringes ±1, ±2, ±3 for dark fringes.
Since the fringes are equally spaced the distance between two consecutive bright or consecutive dark fringes gives fringe width.
