This is a question directly from a homework sheet, however I can't find any decent answers online so hopefully someone can help!

In single slit diffraction, why is the central maximum double the width of the other bands and the brightest?

I understand vaguely that it is something to do with Fresnel zones, but I'm quite confused. Instead of making another question, I think this question also fits in with the above:

Why does the intensity of light bands decrease away from the central maximum in single slit diffraction?

Thanks!