Question

what kind of fringes do you expect to observe off-white light is used instead of monochromatic light.

Answer 1

White light consists of waves of inumerable wavelengths starting from violet to red colour. Therefore if monochromatic light in Young’s interference experiment is replaced by white light, then the waves of each wavelength form their separate interference patterns. The resultant effect of all these patterns is obtained on the screen.

Answer 2

White light comprises of rushes of innumerable wavelengths beginning from violet to red shading. In this way on the off chance that monochromatic light in Young's impedance try is supplanted by white light, at that point the floods of every wavelength structure their different obstruction designs.

The resultant impact of every one of these examples is acquired on the screen.