Physics Maxima and Minima increase or decrease or stay the same ?

Question

Does the distance between maxima increase or decrease or stay the same when the slit separation is increased? when the slit width is increased? what about minima?

thanks for any help to understand how this works.

Answer 1

In multislit diffraction/interference you have the 1-slit diffraction response as a limiting envelope for for the multislit interference peaks. As slit separation d increases, it takes less of an angle change to get 1 wavelength path length change, so the distance between interference peaks decreases. For similar reasons, as slit width a increases, the distance between the maxima of the limiting envelope decreases. When maxima spread apart, so do minima. Maxima are most often considered when dealing with the interference response, while minima are more generally considered with respect to 1-slit diffraction envelope response. This is because interference maxima and diffraction minima occur at integer multiples of distance (ni) from the center whereas interference minima and diffraction maxima occur at integer + 0.5 multiples of distance (ni+0.5) from the center (except there is no diffraction maximum at 0+0.5).
I suggest the ref. web page and other pages it links to to get a better grasp of the diffraction phenomenon.