Physicists Modify Double-Slit Experiment to Confirm Einstein's Belief
Posted on Monday, March 12, 2007 @ 22:05:48 UTC by vlad
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Work completed by physics professors at Rowan University shows that
light is made of particles and waves, a finding that refutes a common
belief held for about 80 years.
Shahriar S. Afshar, the visiting professor who is currently at Boston's
Institute for Radiation-Induced Mass Studies (IRIMS), led a team,
including Rowan physics professors Drs. Eduardo Flores and Ernst
Knoesel and student Keith McDonald, that proved Afshar’s original
claims, which were based on a series of experiments he had conducted
several years ago.
An article on the work titled "Paradox in Wave-Particle Duality" recently published in Foundations of Physics,
a prestigious, refereed academic journal, supports Albert Einstein’s
long-debated belief that quantum physics is incomplete. For eight
decades the scientific community generally had supported Niels Bohr’s
ideas commonly known as the Copenhagen Interpretation of Quantum
Mechanics. In 1927, in his “Principle of Complementarity,” he asserted
that in any experiment light shows only one aspect at a time, either it
behaves as a wave or as a particle. Einstein was deeply troubled by
that principle, since he could not accept that any external measurement
would prevent light to reveal its full dual nature, according to
Afshar. The fundamental problem, however, seemed to be that one has to
destroy the photon in order to measure either aspects of it. Then, once
destroyed, there is no light left to measure the other aspect.
“About 150 years ago, light was thought to behave solely as a wave
similar to sound and water waves. In 1905, Einstein observed that light
might also act as being made out of small particles. Since then
physicists found it difficult understanding the full nature of light
since in some situations it acts like a particle and in others like a
wave,” Flores said. “This dual nature of light led to the insight that
all fundamental physical objects include a wave and a particle aspect,
even electrons, protons and students.”
Afshar conducted his initial theoretical and experimental work at
IRIMS, where he served the privately funded organization as a principal
investigator. He later continued his work at the Harvard University
Physics Department as a research scholar, where he was able to verify
his initial findings before going to Rowan.
In 2004, Afshar claimed that he had devised an experiment that
challenged Bohr’s principle of complementarity. The Rowan team was
formed to verify Afshar’s claim at extremely low light intensity
levels. Afshar, Flores and Knoesel conducted experiments at Rowan that
validated Afshar’s initial findings for single photons.
In this modified double-slit experiment, a laser beam hits a screen
with two small pinholes. As a particle, light goes through one of the
pinholes. Through a lens system, the light is then imaged onto two
detectors, where a certain detector measures only the photons, which
went through a particular pinhole. In this way, Afshar verified the
particle nature of light. As a wave, light goes through both pinholes
and forms a so-called interference pattern of bright and dark fringes.
“Afshar’s experiment consists of the clever idea of putting small
absorbing wires at the exact position of the dark interference fringes,
where you expect no light,” Knoesel said. “He then observed that the
wires do not change the total light intensity, so there are really dark
fringes at the position of the wires. That proves that light also
behaves as a wave in the same experiment in which it behaves as a
particle.”
The findings of the Afshar experiment were published online on January 23 in the Foundations of Physics,
an international journal devoted to the conceptual bases and
fundamental theories of modern physics, biophysics and cosmology, with
several distinguished Nobel laureates on its editorial board. The print
version was published in the February 2007 edition and is now available
in libraries throughout the world.
“The important new contribution is that light carries both wave and
particle aspects at all times, and future experiments will further
clarify the nature of each component.” Afshar said.
Flores continued, “It is interesting to note that even after 80
years we can still gain a better understanding about the nature of
light using refined measurement techniques and creative ideas and
therefore are able add to the vast insights of former scientists.”
Citation: Paradox in Wave-Particle Duality, Shahriar S. Afshar, Eduardo Flores, Keith F. McDonald and Ernst Knoesel, Foundations of Physics, 23 January 2007, DOI 10.1007/s10701-006-9102-8
Source: Rowan University
Via: http://www.physorg.com/news92937814.html
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