What does "minimum range of uncertainty" mean in QM?

[Summer95]

Homework Statement

[/B]
The problem on where the photon will hit a screen, after passing through a single horizontal slit.

I know the wavelength, slit width, magnitude of momentum of incoming photon (calculated), and distance between screen and slit.

Homework Equations

I just don't understand what the question is asking. What does minimum range of uncertainty mean?

 

[vela]

If you send a bunch of photons through the slit, you'll get a spot on the screen. The problem is essentially asking you to find the size of that spot. There's a limit to how small the spot will be because of the uncertainty in the component of the photon's momentum parallel to the slit.