Final answer:
While it is possible for a single slit to not have a distinct minimum in the interference pattern if the slit width is very large, double slits and diffraction gratings always have clear minima due to their multiple slits or lines causing interference.
Step-by-step explanation:
It is possible that there is no minimum in the interference pattern of a single slit if the slit width is very large compared to the wavelength of the light. In such a case, the diffraction pattern would not be distinct enough to observe clear minima. However, for double slits and diffraction gratings, the interference patterns always have minima due to the constructive and destructive interference of light waves passing through multiple slits or grating lines.
Double slits and diffraction gratings produce very similar interference patterns with clear minima and maxima. The difference is that diffraction gratings have narrower and sharper maxima. Single-slit patterns are distinguished by a larger central maximum and smaller, less intense maxima to the sides, and minima that can become indistinct if the slit width is too large.