The fringe-width in Young’s experiment, when the separation between the slits is $0.5 \mathrm{mm}$ and the distance of the screen from the slits in $1.5 \mathrm{m}$, is $1.8 \mathrm{mm}$. Find the path difference between the interfering waves at the position of first-order maximum.

Two waves of equal amplitudes and wavelengths but differing in phases are superimposed. The amplitude of the resultant wave is maximum when phase difference is:

For constructive interference to take place between two monochromatic light waves of wavelength $\lambda$, the path difference should be:

Young’s double-slit arrangement is contained in a transparent chamber. If the chamber is evacuated, then:

When sodium lamp in Young’s double-slit experiment is replaced by an ordinary bulb (white light), then: