In a certain double slit experimental arrangement, interference fringes of width 1.0 mm each are observed when light of wavelength 5000 Å is used. Keeping the set-up unaltered if the source is replaced by another of wavelength 6000 Å, the fringe width will be:
a. 0.5 mm
b. 1.00 mm
c. 1.2 mm
d. 1.5 mm