I made an error in my explanation. A single slit does not produce an interference pattern but rather a diffraction pattern. Allow me to clarify the distinction between interference and diffraction in the context of the double-slit experiment.
In the double-slit experiment, when both slits are open, the observed pattern on the screen is indeed an interference pattern. This pattern arises due to the interference of waves generated by the particles passing through the two slits. Each particle behaves as a wave, and these waves interfere with each other, resulting in the characteristic pattern of alternating bright and dark fringes.
On the other hand, when a single slit is used instead of two slits, the resulting pattern on the screen is a diffraction pattern. Diffraction occurs when waves encounter an obstacle or aperture and bend around it, spreading out and interfering with each other.
When a beam of particles, such as photons or electrons, passes through a single slit, the wave nature of the particles causes them to diffract. The diffracted waves then spread out and interfere with each other, resulting in a pattern of alternating bright and dark regions on the screen. This diffraction pattern is distinct from the interference pattern observed in the double-slit experiment.
The central bright region in the diffraction pattern corresponds to the most intense part of the wave, while the surrounding dark regions occur due to destructive interference, where the peaks of one part of the wave cancel out the troughs of another part.
So, to clarify, a single slit in the double-slit experiment produces a diffraction pattern, while the interference pattern is observed when both slits are open and the waves from each slit interfere with each other.