To reduce the distance between adjacent bright fringes in a double-slit interference experiment, which single adjustment listed below would be most effective if all other variables remain unchanged?
(a) Double the distance between the slits and the screen from 1.0 m to 2.0 m.
(b) Halve the slit separation from 0.30 mm to 0.15 mm.
(c) Double the slit separation from 0.30 mm to 0.60 mm.
(d) Replace the 650 nm laser with a 780 nm laser.