In Young's experiment, light of wavelength 4000 Å is used to produce bright fringes of width 0.6 mm, at a distance of 2 meters. If the whole apparatus is dipped in a liquid of refractive index 1.5, then fringe width will be

• A

  0.2 mm

• B

  0.3 mm 

• C

  0.4 mm

• D

  1.2 mm