Answer:
b. 0.25cm
Explanation:
You can solve this question by using the formula for the position of the fringes:
[tex]y=\frac{m\lambda D}{d}[/tex]
m: order of the fringes
lambda: wavelength 500nm
D: distance to the screen 5 m
d: separation of the slits 1mm=1*10^{-3}m
With the formula you can calculate the separation of two adjacent slits:
[tex]\Delta y=\frac{(m+1)(\lambda D)}{d}-\frac{m\lambda D }{d}=\frac{\lambda D}{d}\\\\\Delta y=\frac{(500*10^{-9}nm)(5m)}{1*10^{-3}m}=2.5*10^{-3}m=0.25cm[/tex]
hence, the aswer is 0.25cm