How far apart can slits be in double slit experiment to still show interference?

[Pjpic]

About how far apart can the slits get, in the double slit experiment, and still show the interference pattern?

 

[ShayanJ]

It should be comparable to the wavelength of the light. If you increase it to values significantly higher than that, there will be no interference pattern. In fact the pattern becomes smaller and smaller until at first your eyes and then your detectors don't have the required resolution to perceive it.

 

[jtbell]

In fact the pattern becomes smaller and smaller

More precisely, the maxima (peaks) become narrower and narrower, and spaced closer and closer together.