Monochromatic light from a distant source is incident on a

Question

I need proficient help in the following problem:

Problem: Monochromatic light from a distant source is incident on a slit 0.730mm wide. On a screen 2.10m away, the distance from the central maximum of the diffraction pattern to the first minimum is measured to be 1.20mm

Part I. Calculate the wavelength of the light.

Answer in nm

I want you to explain the physics in this problem