In the double-slit experiment, the interference pattern appears as a series of bright and dark regions rather than two distinct slits because of the wave-like nature of particles, such as electrons or photons.
When a beam of particles (e.g., electrons) passes through two closely spaced slits, each slit acts as a source of a new wavefront. These waves propagate outward from the slits and overlap with each other. This phenomenon is known as interference.
Interference occurs when the peaks of one wave align with the peaks of another wave, resulting in constructive interference and producing bright regions called fringes. Conversely, when the peaks of one wave align with the troughs of another wave, destructive interference occurs, resulting in dark regions.
The interference pattern arises because each particle can be described by a probability wave or wavefunction, which determines the likelihood of the particle being detected at a particular location. The wavefunctions from each slit interfere with each other, leading to regions of constructive and destructive interference.
When the interference pattern is observed on a screen or detector placed after the double slits, the bright fringes correspond to regions where the waves interfere constructively, resulting in a higher probability of particle detection. The dark regions, on the other hand, correspond to regions of destructive interference, where the waves cancel each other out, resulting in a lower probability of particle detection.
Thus, the interference pattern appears as a series of bright and dark dots because it represents the distribution of particle detections resulting from the wave-like interference of the particles passing through the double slits.