In Young’s double slit experiment the separation d between the slits is 2 mm, the wavelength λ of the light used is 5896 A0 and distance D between the screen and slits is 100 cm. It is found that the angular width of the fringes is 0.200. To increase the fringe angular width to 0.210 (with same λ and D) the separation between the slits needs to be changed to