Answer:
Blue light
Explanation:
y=Lwm/d
where:
y is the distance between the finges
w is the wavelength is light (I dont have a symbol for lambda)
m is the fringe order (the central bright fringe is the zeroth- order, the next on either side is the + or - first order, et cet)
d is the distace between the slits
So to reduce y, the spacing between the fringes, you could move your screen closer to the slits, use slits that are spaced farther apart, or use a shorter wavelength of light (shift toward the blue)
