Roy J. Glauber

wave-particle duality


Light, wave and corpuscle. Two different theories converge thanks to quantum physics
wave duality corp; sculo , also called particle wave, resolved an apparent paradox , demonstrating that light and the matter may, in turn, own property particle and wave properties.
According to the classical physics differences between wave and particle. A particle occupies a place in space and has mass while a wave spreads in space characterized by having a speed defined mass and void.
Now considered to be the wave duality - particle is a "concept of quantum mechanics according to which there are no fundamental differences between particles and waves: the particles can behave as waves and vice versa." ( Stephen Hawking 2001 )
This is a fact proven experimentally on many occasions. It was introduced by Louis de Broglie , French physicist of the early twentieth century. In 1924 in his doctoral thesis proposed the existence of waves of matter, namely that all matter was a wave associated with it. This revolutionary idea, based on analogy with the radiation had a particle associated property and then demonstrated, not aroused great interest, despite the soundness of its approach, because no evidence was produced. However Einstein recognized its importance and five years later in 1929 , received the Nobel Prize in physics for their work.
His work said that wavelength , the wave associated with the matter was

where h is Planck's constant and p is momentum of the particle of matter.
History

At the end of the nineteenth century , thanks to atomic theory is Saturday , to which all matter was composed of elementary particles called atoms . The electricity thought first as a fluid , but Joseph John Thomson showed that consisted of a stream of particles called electrons , in their experiments with . All these discoveries led to the idea that a large part of Nature was composed of particles. At the same time, waves were well understood, together with its phenomena, such as diffraction and interference . It was believed therefore that the light was a wave, as demonstrated by the Experiment Young and effects such as Fraunhofer diffraction .
When reached twentieth century , however, appeared problems with this viewpoint. The photoelectric effect , as analyzed by Albert Einstein in 1905 , showed that light also possessed properties of particles. Later, diffraction of electrons was predictable and demonstrated experimentally, thus, the electrons owned properties that were ; been attributed both to an particles and waves.
This confusion facing, apparently, the properties of particles and waves was resolved by the establishment of the quantum mechanics in the first half of the twentieth century. Quantum mechanics serves as a framework for unified work to understand that all matter may have properties of wave and particle properties. Every particle of nature, is a proton , a No atom or which was, described by a differential equation usually Schringer Equation . The solutions to these equations are known as wave functions , since they are inherently wave in form. Diffracted and can interfere, leading us to wave and the effects observed. In addition, the wave functions are interpreted as descriptors of the probability of finding a particle at a given point in space. This means that if you look for a particle, will meet with a probability given by the square root of the wave function.
In the macroscopic world are not observed wave properties of objects such as wavelengths , as in humans, are too small. The wavelength is, in essence, as the inverse of the size of the object multiplied by the Planck's constant h , an extremely small number.
Huygens and Newton
Early theories of light were understandable given by Christiaan Huygens , who proposed a wave theory of the same, and in particular, proving that every point a wavefront progresses is indeed the center of a new perturbaciy the source of a new train of waves. However, his theory was weak at other points and was soon overshadowed by the Theory corpuscular Isaac Newton . In it, Newton proposed that light consisted of small particles, which could easily explain the phenomena of reflection . With a little more difficulty, Newton could also explain the refraction through lenses and the separation of sunlight into colors through a prism .
Because of the enormous intellectual stature of Newton, his theory was the dominant for a period of about a century, while the theory Huygens was forgotten. With the discovery of diffraction in nineteenth century , however, the wave theory was recovered during the twentieth century and the debate between the two survived for a long time.
Fresnel, Maxwell & Young
At the beginning of nineteenth century , with the experiment double slit Young and Fresnel certified scientific theories Huygens. The experiment showed that light, when going through a slit, shows a pattern characteristic of interference similar to waves produced in water. The wavelength can be calculated using those patterns. Maxwell , at the end of that century, explained light as the spread of a electromagnetic wave through Maxwell's equations . Such equations, amply demonstrated by the experience, which made Hugens was again accepted.
Einstein and photons

Effect fotoelctrica: The light starts electrons of the plate
1905 Einstein achieved a remarkable explanation of photoelectric effect , an experiment until then worrying that the theory wave was unable to explain. He did postulate the existence of photons how many of with properties of light particles.
In the photoelectric effect was observed that if a beam of light impacted on a metal plate produced Electricity in the circuit. Presumably, the light liberating electrons in the metal, causing its flow. However, while a blue light was weak enough to cause this effect, even stronger and more intense red light is not caused. According to the wave theory, the strength or breadth of light was in proportion with its brilliance: The brightest light should be more than enough to create the passage of electrons through the circuit . However, strangely, did not produce.
Einstein concluded that electrons were expelled out of metal in the incidence of photons. Each individual photon entailed a lot of energy E, which was related frequency of light, using the following equation:

Where h is the Planck (6,626 x 10 -34 J second). Only photons with high frequency (above a threshold value specific) could cause the flow of electrons. For example, the blue light emitted few photons with an energy enough to boot the electrons of the metal, while the red light did not. A more intense light above the minimum threshold can boot more electrons, but no amount of light below the same may start one, no matter how intense it is their brightness.
Einstein won Nobel Prize in Physics in 1921 by his theory of photoelectric effect.
De Broglie

In 1924 , physical French Louis de Broglie ( 1892 - 1987 ), made a hypothesis in stating that:
entire field features both wave corpusculares as behaving in one way or another depending on the specific experiment .
To apply this property of matter De Broglie was based on the explicacci photoelectric effect , shortly before had Albert Einstein suggesting nature quantum of light. For Einstein, energy carried by light waves was quantization, distributed in small packages ENERGY light quanta, that later would be called photons , and whose power depended on the frequency of light across the relationship: where is the frequency of the light wave and Planck's constant . Albert Einstein proposed in this way, which in certain processes electromagnetic waves that make light behave like corpuscles. De Broglie wondered why it could not be any way reverse, ie a particle material (one corpuscle) could show the same behavior that a wave.
The physical French related wavelength , (lambda) with amount of movement of the particle, using the formula:
, where
is the length of wave associated with the particular mass m that moves at a speed v , and h is Planck's constant. The product is also the form of the vector, or momentum of the particle. Displaying the formula is very easy to see that as the mass of the body or increases its speed significantly reduces the wavelength.
This hypothesis was confirmed three years later for the electrons , observing the results of double slit experiment Young in diffraction electron into two independent investigations. The University of Aberdeen George Paget Thomson rose , An electron beam across a thin metal plate and noted the different schemes predicted. In Bell Laboratories Clinton Davisson and Halbert Lester Germer guided his beam across a cell crystal.
The equation of De Broglie can be applied to all the matter. The macroscopic bodies, would also have associated a wave, but, given that its mass is very large, the wavelength is so small that they do not appreciate their wave characteristics.
De Broglie was Nobel Prize in Physics in 1929 by this hypothesis. Thomson and Davisson shared the Nobel 1937 for his experimental work.
Nature wave of objects larger
Similar experiments have been repeated with neutrons and protons , the most famous of them carried out by Estermann and Otto Stern in 1929 . Most recent experiments conducted with atoms and molecules show that also act as waves.
A series of experiments emphasizing the action of gravity in connection with the dual wave-corpuscle were made in decade of the 70 using a neutron interferometer . The neutrons, part of nucleus constitute much of the mass the same and therefore the matter. The neutrons are fermions and this, in a sense, are the quintessence of particles. But in the neutron interferometer, not only acting as waves mecanocuticas but also those waves were directly under the force of gravity . While this was no surprise, since they knew that gravity could deflect light and even acted on photons (The failed experiment on the photons Pound-Rebka ), had never been observed before acting on the airwaves of mecanocuticas fermions, the constituents of ordinary matter.
1999 was reported diffraction of fullerene C ₆₀ by researchers at the University the Vienna . ^[1] The fullerene is a massive object, with a atomic mass of 720. The wavelength of de Broglie is 2.5 Picometre , while the molecular diameter is 1 nanometer , that is 400 times higher. Until 2005 , this is the largest object on which properties have been observed ondaluatorias mecanocuticas so direct. The interpretation of these experiments still creates controversy since it was assumed the arguments of the wave-particle duality and the validity of the equation de Broglie in its formulation.
Teory philosophy
The paradox duality of the wave-corpsculo is resolved in the theoretical framework of the quantum mechanics . It is deep and complex, as well as impossible to summarize briefly.
Each particle in nature, is photon electron atom or whatever, can describrise in terms of the settlement of a differential equation , typically the Schringer equation , but also the Dirac equation . These solutions are function calls wave functions . The wave functions can diffracted and interfere with others or with themselves, as well as other phenomena ondulatios predictable described in double slit experiment .
The wave functions are often interpreted as probability to find the corresponding particle at a given point of space at any given time. For example, in an experiment that contains a particle moving, one can find the particle that reaches a particular location at a given time using a detection device to point to that place. While the quantum behavior follows a deterministic well-defined functions (such as wave functions), such solutions are probability equations. The probability that the detector is the particle is calculated using the integral product of the wave function and its complex conjugate . While the role of wave propagation can be thought of as a particle in space, in practice the detector see or not see particle whole issue, may never see a portion thereof, as two-thirds of an electron. Behold the strange duality: The particle spreads in space on a wave and probabilistic but reaches the detector as a corpuscle complete and localized. This paradox has conceptual explanations in the form of Copenhagen Interpretation , Way Formulation of the Comprehensive or Theory of Many Worlds . It is important to point out that all these inteprpretaciones are equivalent and are in the same prediction, despite offering some interpretations philosophical very different.
While quantum mechanics makes accurate predictions on the outcome of such experiments, its meaning is still looking for philosophical and discussed. That debate has evolved as an extension of the effort to understand the duality wave-corpuscle. What siginifica for a proton behave as wave and particle? How can it be a antielectr mathematically equivalent to an electron moving backwards in time under certain circumstances, and what implications does this have to our experience of unidirectional time ? How can a particle teleportation through a barrier while a soccer ball can not pass through a concrete wall? The implications of these facets of quantum mechanics are still baffled many of those who are interested in it.
Some physicists intimately related to the effort to achieve the rules of mechanical ; quantum nica have seen this philosophical debate about the duality wave-corpuscle as attempts to overlay human experience in the quantum world. Since, by nature, this world is not completely intuitive, quantum theory must be learned under its own terms independent of the experience based on intuition of the macroscopic world. The scientific merit of looking so deeply for a meaning to quantum mechanics is, for them, suspect. The Bell's theorem and experiments that inspires are a good example of finding the foundations of quantum mechanics. From the viewpoint of a physicist, the inability of the new philosophy of quantum satisfy a criterion ascertainable or their inability to find a fault in the predictability of the current theories reduced to a position zero, even at risk of degenerating into a pseudoscience .
applicability
The wave duality-corpuscle is used in the electron microscope , where small wavelength associated with electronic n can be used to see objects much smaller than those observed using visible light.