Diffraction due to a narrorw slit

[titan81]

Homework Statement

Light of wavelength 490 nm is incident on a narrow slit. The diffraction pattern is viewed on a screen 3.6 m from the slit. The distance on the screen between the central maximum and the third minimum is 2 cm. What is the width of the slit?

Homework Equations

The Attempt at a Solution

Not sure where I need to start. Can someone help me out

 

[Stonebridge]

You should have in your notes or book, a formula ("single slit diffraction")for the angular positions of the various minima. This formula has the width of slit, the wavelength of the light, the number of the minimum counted from the centre, and the sin of the angle.
You can work out the angle from the distances given in the question, so you know all the quantities bar the width of the slit.