Answer:
0.126mm
Explanation:
To find the distance to the central bright spot you can use the following formula:
y: distance from the m-bright spot to the central one.
m: order of the bright (in this case, the second order, m=2)
D: distance to the scree = 1.6m
d: distance between slits = 17mm = 17*10^{-3}m
By replacing the values of m, D, d and the wavelength you obtain:
hence, the ditance from the second order fringe to the central spot is 0.126mm