A Young's double slit experiment is conducted using white light.

Step-by-step solution

In a Young's double slit experiment using white light, the central fringe is formed where the path difference x = 0 for all wavelengths. Since all colors interfere constructively at this point, the central fringe appears white. For a completely dark fringe to form, destructive interference must occur simultaneously for all wavelengths at the same position. This requires the path difference to be an odd multiple of 2 for all wavelengths, which is impossible. Therefore, there will be no completely dark fringe. As we