Given a slit of width `w` and a light source with wavelength `lambda`,
the diffraction pattern will be given by the formula:

lambda
sin( theta ) = m --------
w

where `m` = 1, 2, 3 .... Solving for `theta` gives you
the angles at which the dark bands in the diffraction pattern appear.

Diffraction is an example of light's wave-like (as opposed to particle-like) behavior.