Two light waves of wavelengths 800 and 600 nm are used in Young's double slit experiment to obtain interference fringes on a screen placed 7 m away from plane of slits. If the two slits are separated by 0 . 35 mm , then shortest distance from the central bright maximum to the point where the bright fringes of the two wavelength coincide will be ______ mm .

Step-by-step solution

Fringe width for both cases can be written as. ω 1 = λ 1 D d   &   ω 2 = λ 2 D d . Using values of wavelength, we get ω 1 = 16   mm   &   ω 2 = 12   mm . Let y be the common distance of the bright fringes by the both wavelength, then y = n 1 ω 1 = n 2 ω 2 . As LCM ω 1 , ω 2 = 48   mm , therefore at y = 48   mm distance both bright fringes will be found.