Q18 of 26 Page 1

In Young’s double slit experiment, the two slits are separated by a distance of 1 �5 mm and the screen is placed 1 m away from the plane of the slits. A beam of light consisting of two wavelengths 650 nm and 520 nm is used to obtain interference fringes. Find

the distance of the third bright fringe for λ = 520 nm on the screen from the central maximum.


the least distance from the central maximum where the bright fringes due to both the wavelengths coincide.


Consider the following diagram.

D = 1m; d = 1.5 × 10-3 m; λ1 = 650 × 10-9 m; λ2 = 520 × 10-9 m


as3.png


Let y be the distance of the third bright fringe from the central maxima.


Let that the ‘n’th bright fringe of 650 nm wavelength coincides with ‘n+1’th bright fringe of 520 nm wavelength at a distance y from the central maximum.








Distance from central maxima =



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