If the double-slit experiment is conducted with only one slit open and electrons as the particles, the interference pattern would not be observed. The interference pattern occurs when there are two slits through which the electrons can pass and interfere with each other.
When only one slit is open, the experiment effectively becomes a single-slit diffraction experiment. In this case, the electrons would diffract as they pass through the single slit, spreading out and creating a pattern of intensity on a screen placed behind the slit. This pattern would exhibit a central maximum and a series of smaller side maxima and minima, known as a diffraction pattern.
However, the diffraction pattern is distinct from the interference pattern observed in the double-slit experiment. In the double-slit configuration, the interference arises due to the superposition of the waves from the two slits, leading to constructive and destructive interference at different points on the screen. With only one slit, there is no second source of waves to interfere with, so the interference pattern would not be present.
In summary, when the double-slit experiment is performed with only one slit open and electrons as the particles, an interference pattern would not be observed. Instead, the diffraction pattern associated with single-slit diffraction would be seen.