With a monochromatic light, the fringe–width obtained in a double–slit experiment is 1.33 mm . if the whole set–up is immersed in water of refractive index 1.33  , the new fringe–width will be

Fringe width β=1.33 mm Refractive index μ=1.33 New fringe width β  '=?                                 β  '=βμ                                      =1.331.33                               β  '=1 mm