DIFFRACTION PROBLEM (physics lab)

[mjsteves]

One of my prelab problems for physics 3:

The Moon is about 4*10^8 m from the Earth and has a diameter of about 3.2*10^6 m. You want a radar antenna which just covers the Moon with the central spot of its diffraction pattern. If the radar wavelength is 10 cm, what is the diameter of the radar antenna?

 

[Redbelly98]

You must make an attempt at solving the problem before receiving help.

What equation or equations do you have that deal with diffraction?