what will happen if white lihgt used in YDSE?

Dear Student,

if white light is used in YDSE instead of a monochromatic light, then the central point is white, although at other places colored fringes will be obtained. The reason for this is that at the centre, path difference is zero for all wavelengths and hence all wavelengths will interfere constructively.

Dear Aspirant,

bright central fringe is formed due to all the colors

fringes of different colors are observed clearly only in the first order as after that dispersion becomes less

the first-order violet fringes are closer to the center of the screen than the first-order red fringes as the wavelength of violet is small .

You can understand that the central fringe itself is white. Fringe width of individual colours is directly proportional to (approximately) the wavelength of the colour. To understand why, it's easy enough. Central fringe is the place on the screen where there is zero optical path difference(or phase difference) between any to waves simultaneously emanating from the two slits. Moving away from the central fringe means there is a difference in distance travelled by such waves to reach the given point. When you move more closer to one of them means you increase the path difference. When you want more change in phase difference for lesser path difference, then wavelength must be smaller. 2 pi times the ratio of path difference to wavelength gives phase difference.

Thank you .

Hello

If white light is used in place of monochromatic light in YDSE then the central point is white although at the other places coloured fringes will be obtained. This is because at the center,  path difference is zero for all wavelength.

Hope my answer will help you

Regards