Question

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 of 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.

Answer 1

Third bright fringe for λ1 = 520 nm is given by

${\displaystyle {\text{x}}_3=\frac{3\lambda \text{D}}{\text{d}}=\frac{3\times 520\times {10}^{-9}\times 1}{1.5\times {10}^{-3}}=1.04\times {10}^{-3}\text{m}}$

= 1.04 mm.