Thinking Again About Large and Small Openings

Remember back at the begining? With large openings electrons behaved more or less as we expected them, as particles, to behave, hitting the screen directly behind the opening. With small openings, however, things got strange, the electrons spread out accross the screen. Now you know enough about phase to understand how this occurs. Click here to bring up the interactive figure we started with.

Imagine a large opening as a series of closely spaced small openings. The amplitude and phase from each part of this large opening add giving a varying total probability on the screen. Because of destructive interference the probability of finding a particle at the edges of the screen is lower than that at the center. You can see the destructive addition of amplitudes in the progressive non-alignment of the vectors appearing as as the decreasing length of the the total amplitude vector on the right. With smaller openings, the destructive interference pattern spreads out to yield the unexpected quantum behavior that we started with.

In short, the quantum world and the classical world need not be thought of as totally different. With a single set of ideas including the concepts of exploring all paths and of phase, both worlds, and a continuity of worlds between them, can all be accounted for equally well.