Question $7$: The figure below depicts the double$-$slit experiment set up$.$ However, the light source is a white light

consisting of a mixture of monochromatic lights with the various wavelengths. What will be the predominant color of

he fringe observed at the point $P$ on the screen? Also, $S_{2}P-S_{1}P=\frac{{}_b}{2},$ where ${}_b$ is the wavelength of blue color.