How Does Light Intensity Vary with One Slit in a Diffraction Experiment?

[Vaseline]

If one slit is used instead of 2 in a diffraction experiment, how does light intensity vary?

I think.. Central fringe brighter, symmetrical fringes either side of central fringe, central maximum twice the width of side fringes..

But I'm not sure why?

Also, using diffraction gratings – why is the maximum brightness in the middle?

 

[diazona]

Think about why fringes exist at all when you have 2 slits. Does the same reasoning apply with 1 slit?