How does one electron go through two slits at the same time? In Young's Double-Slit experiment
Hawking, Feynman and Brian Greene say that one electron goes through both slits at the same time.
Asked by: Donald Lem
If you picture an electron as merely a point particle travelling like a billiard ball
through space, it is impossible to imagine one travelling through two slits at once; but
the quantum universe of the very small is not just a miniature version of reality as we
perceive it at our macro level of understanding. The electron as a small particle is merely
a model of reality that helps us visualize some of its behaviors, but obviously not all of
Light passing through 2 slits an appropriate distance apart vs. its wavelength displays
a diffraction pattern of light and dark patches beyond the slits. Since the photoelectric
effect and other experiments can best be explained by treating light as made of particles
called photons, one could also ask how a photon can travel through two slits at once. The
so-called 'duality' nature of light as both wave and particle applies to electrons as well.
While electrons behave like point particles in some experiments, they can demonstrate a
wavelike behavior in others. DeBroglie showed that any mass in motion can also be
described by a wave, but most objects are much too large for that wave behavior to be
observed because wavelength is inversely proportional to mass. The low mass of the electron
does allow its wave behavior to be observed, as it is in the two slit experiment.
The wavelike nature of electrons also makes possible electron microscopes, which can resolve
finer details than light microscopes because of the smaller wavelength of their waves.
Answered by: Paul Walorski, B.A. Physics, Part-time Physics Instructor
Just to clarify one point, if a single photon is fired at the two slits,
pattern will not appear. Rather, a single 'blip' will appear on the
screen, which indicates
that the photon is not a wave, but rather a particle. If a large
number of photons
are fired at the slits,an interference pattern will begin to appear.
So it seems that
photons are really particles that behave collectively like waves. The
reasoning applies to all particles, not just photons.
Answered by: R. Walkup
'One thing I have learned in a long life: that all our science, measured against reality, is primitive and childlike - and yet it is the most precious thing we have.'