What is the effect on the interference fringes in a Young.s double-slit experimental due to each of the following operations :
The monochromatic source is replaced by a source of white light?

Explanation

The interference patterns due to different component colours of white light overlap (incoherently). The central bright fringes for different colours are at the same position. Therefore, the central fringe is white. For a point P for which `S_(2)P-S_(1)P= lambda_(b)"/"2`, where `lambda_(b)(= 4000 dotA)` represents the wavelength for the blue colour, the component will be absent and the fringe will appear red in colour.
Slightly farther away where `S_(2)Q-S_(1)Q= lambda_(b)= lambda_(r )"/"2` where `lambda_(r )(approx 8000 dotA)` is the wavelength for the red colour, the fringe will be predominantly blue.
Thus, the fringe closest on either side of the central white fringe is red and the farthest will appear blue. After a few fringes, no clear fringe pattern is seen.