Question

In a Young’s double-slit experiment, a beam of light consisting of two wavelengths 500 nm and 600 nm is used. The interference fringes are observed at a screen placed 1.8 m away from the plane of slits (slit separation 0.3 mm). Calculate the least distance from the central maximum where the bright fringes due to both the wavelengths coincide.

Hint:

For two wavelengths in YDSE: First find LCM condition \(n_1\lambda_1 = n_2\lambda_2\), then substitute in fringe formula.

Answer 1