Click here to go to the Physics Virtual Bookshelf home page. Here we briefly outline some of the key features of these developments. Some of the material is well-known, but other parts of what follows are not.
Historical basis of quantum theory Basic considerations At a fundamental level, both radiation and matter have characteristics of particles and waves. The gradual recognition by scientists that radiation has particle-like properties and that matter has wavelike properties provided the impetus for the development of quantum mechanics.
Influenced by Newton, most physicists of the 18th century believed that light consisted of particles, which they called corpuscles. From aboutevidence began to accumulate for a wave theory of light.
At about this time Thomas Young showed that, if monochromatic light passes through a pair of slits, the two emerging beams interfere, so that a fringe pattern of alternately bright and dark bands appears on a screen. The bands are readily explained by a wave theory of light. According to the theory, a bright band is produced when the crests and troughs of the waves from the two slits arrive together at the screen; a dark band is produced when the crest of one wave arrives at the same time as the trough of the other, and the effects of the two light beams cancel.
Beginning ina series of experiments by Augustin-Jean Fresnel of France and others showed that, when a parallel beam of light passes through a single slit, the emerging beam is no longer parallel but starts to diverge; this phenomenon is known as diffraction.
Given the wavelength of the light and the geometry of the apparatus i. However, though the ideas of classical physics explain interference and diffraction phenomena relating to the propagation of light, they do not account for the absorption and emission of light.
All bodies radiate electromagnetic energy as heat; in fact, a body emits radiation at all wavelengths. The energy radiated at different wavelengths is a maximum at a wavelength that depends on the temperature of the body; the hotter the body, the shorter the wavelength for maximum radiation.
Attempts to calculate the energy distribution for the radiation from a blackbody using classical ideas were unsuccessful. A blackbody is a hypothetical ideal body or surface that absorbs and reemits all radiant energy falling on it.
One formula, proposed by Wilhelm Wien of Germany, did not agree with observations at long wavelengths, and another, proposed by Lord Rayleigh John William Strutt of England, disagreed with those at short wavelengths.
In the German theoretical physicist Max Planck made a bold suggestion. He assumed that the radiation energy is emitted, not continuously, but rather in discrete packets called quanta.
Planck showed that the calculated energy spectrum then agreed with observation over the entire wavelength range. Furthermore, emission takes place as soon as the light shines on the surface; there is no detectable delay.
Einstein showed that these results can be explained by two assumptions: The spectra of light emitted by gaseous atoms had been studied extensively since the midth century.
It was found that radiation from gaseous atoms at low pressure consists of a set of discrete wavelengths. This is quite unlike the radiation from a solid, which is distributed over a continuous range of wavelengths. The set of discrete wavelengths from gaseous atoms is known as a line spectrumbecause the radiation light emitted consists of a series of sharp lines.
The wavelengths of the lines are characteristic of the element and may form extremely complex patterns. The simplest spectra are those of atomic hydrogen and the alkali atoms e. For a given value of m, the lines for varying n form a series.
The model was based on the experiments of Hans Geiger and Ernest Marsdenwho in bombarded gold atoms with massive, fast-moving alpha particles; when some of these particles were deflected backward, Rutherford concluded that the atom has a massive, charged nucleus.Quantum theory is the theoretical basis of modern physics that explains the nature and behavior of matter and energy on the atomic and subatomic level.
The nature and behavior of matter and energy at that level is sometimes referred to as quantum physics and quantum mechanics. Planck wrote a. The subject of most of this book is the quantum mechanics of systems which have a small number of degrees of freedom.
This book is a mix of descriptions of quantum mechanics itself, the general properties of systems described by quantum mechanics, and general techniques for . Quantum mechanics, science dealing with the behaviour of matter and light on the atomic and subatomic scale. It attempts to describe and account for the properties of molecules and atoms and their constituents—electrons, protons, neutrons, and other more esoteric particles such as quarks and.
Quantum mechanics is a physical science dealing with the behaviour of matter and energy on the scale of atoms and subatomic particles / waves. Understanding exactly what this property was, and why it was quantised, was a major part in the development of quantum mechanics, as shown in the rest of this article.
The Development of Quantum MechanicsOverviewQuantum mechanics describes the relationship between energy and matter on an atomic and subatomic scale. At the beginning of the twentieth century, German physicist Maxwell Planck () proposed that atoms absorb or emit electromagnetic radiation in bundles of energy termed quanta. This quantum . Applications of quantum mechanics. As has been noted, quantum mechanics has been enormously successful in explaining microscopic phenomena in all branches of heartoftexashop.com three phenomena described in this section are examples that demonstrate the quintessence of the theory. Quantum mechanics, science dealing with the behaviour of matter and light on the atomic and subatomic scale. It attempts to describe and account for the properties of molecules and atoms and their constituents—electrons, protons, neutrons, and other more esoteric particles such as quarks and.
Introduction to Quantum Mechanics "Microscopic World – Introduction to Quantum Mechanics." by Takada, Kenjiro. The Development of Quantum Mechanics.
Click here to go to the UPSCALE home page. Click here to go to the Physics Virtual Bookshelf home page. Introduction. Working essentially independently, in the mid's Heisenberg and Schrödinger both created a full form of Quantum Mechanics.