Single-slit Diffraction

[Alice-Shallom]

Hi,
I need help with the following:

Prove that if the wavelength of light is equal to or greater than the width of a slit, light striking the slit perpendicularly passes through without forming any dark interference bands.

[Tony Zalles]

I think our AP Physics talked about something like that towards the end of the year...but by that time Senioritis was in full effect...lol