Chapter 28 - Physical Optics: Interference and Diffraction - Problems and Conceptual Exercises - Page 1008: 83

$24.4Km$

We can find the required distance as follows: $L=\frac{y}{tan\theta_{min}}$ $\implies L=\frac{y}{tan(1.22\frac{\lambda}{D})}$ We plug in the known values to obtain: $L=\frac{1.32m}{tan(1.22\times\frac{555\times 10^{-9}m}{12.5\times 10^{-3}m})}$ $L=24.4\times 10^3m=24.4Km$