Q10.6 A beam of light consisting of two wavelengths, 650 nm and 520 nm, is used to obtain interference fringes in a Young’s double-slit experiment.
(b) What is the least distance from the central maximum where the bright fringes due to both the wavelengths coincide?
Let the nth bright fringe due to wavelength, and (n − 1)thbright fringe due to wavelength coincide on the screen. We can equate the conditions for bright fringes as:
Hence, the least distance from the central maximum can be obtained by the relation:
Hence we can find out X if D and d are given.