Quantum theory photoelectric effect

Albert Einstein s 1905 work on the photoelectric effect paved the way for one of the greatest advances of twentieth-century science, the theory of quantum mechanics. Light had always been regarded as a wave. Quantum mechanics introduced the concept of light being transmitted in wave packets, or photons, that have particle-like qualities as well as wave-like qualities. 

Experimental chemists are rarely concerned with quantum effects and it s not unusual to find them ignoring this fundamental theory altogether. Even when an effort is made to explore the topic more deeply traditional quantum phenomena like black-body radiation, Compton scattering and even the photoelectric effect may appear to be of somewhat limited importance. Experimentalists who rely on spectroscopic measurements get by with interpretations based on a few simple semi-classical rules, and without ever appreciating the deep significance of quantum theory. Maybe there is a problem with the rigorous mathematical formulation of quantum theory and too little emphasis on quantum effects routinely encountered in chemistry. 

Schrodinger s equation is widely known as a wave equation and the quantum formalism developed on the basis thereof is called wave mechanics. This terminology reflects historical developments in the theory of matter following various conjectures and experimental demonstration that matter and radiation alike, both exhibit wave-like and particle-like behaviour under appropriate conditions. The synthesis of quantum theory and a wave model was first achieved by De Broglie. By analogy with the dual character of light as revealed by the photoelectric effect and the incoherent Compton scattering... 

Besides the complementary discoveries of radioactivity and X rays, the period of Duchamp s intellectual formation saw the announcement of electrons, the photoelectric effect, quantum theory, the theory of relativity, wireless telegraphy, and other amazing, truly scientific revelations. Following one another in quick succession, they officially established in strictly scientific terms novel perceptual premises already fashioned by avant-garde painters of the Symbolist, then Expressionist and Cubist camps. Like the most advanced artists of the period, physicists and chemists alike now seemed bent upon esoteric explorations beyond (aw-delh) the realm of the merely visible, and thus the rational element previously taken to be latent in every nook and cranny belonging to the physical world was now made potentially mysterious. Now it was official perception was itself only relative accordingly, reality itself had to be redefined. 

The Maxwell-Heaviside theory seen as a U(l) symmetry gauge field theory has no explanation for the photoelectric effect, which is the emission of electrons from metals on ultraviolet irradiation [39]. Above a threshold frequency, the emission is instantaneous and independent of radiation intensity. Below the threshold, there is no emission, however intense the radiation. In U(l), electrodynamics energy is proportional to intensity and there is, consequently, no possible explanation for the photoelectric effect, which is conventionally regarded as an archetypical quantum effect. In classical 0(3) electrodynamics, the effect is simply... 

Fortunately for science, Einstein s deflection toward other problems ended productively, for the ensuing 1905 Annus Mirabilis witnessed publication of Einstein s three papers on the special theory of relativity, Brownian motion, and the quantum theory of the photoelectric effect.)... 

Sommerfeld applied the theory of quanta to the emission of X- and y-rays, to the photoelectric effect, and sketched the theory of the ionization potential. At the beginning of his paper he discussed in some detail the relationship observed in the emission of X- (or y-) rays by cathode (or 0) rays and arrived at the conclusion that large quantities of energy are emitted in shorter times and small quantities of energy in larger times. 9 According to Sommerfeld this empirical result speaks in favor of the central role played in atomic and molecular phenomena by the quantum of action h introduced by Planck, the dimensions of which are energy multiplied by time. 

The first inference of photon mass was made by Einstein and de Broglie on the assumption that the photon is a particle, and behaves as a particle in, for example, the Compton and photoelectric effects. The wave-particle duality of de Broglie is essentially an extension of the photon, as the quantum of energy, to the photon, as a particle with quantized momentum. The Beth experiment in 1936 showed that the photon has angular momentum, whose quantum is h. Other fundamental quanta of the photon are inferred in Ref. 42. In 1930, Proca [43] extended the Maxwell-Heaviside theory using the de Broglie guidance theorem ... 

C. Dewdney, A. Garuccio, A. Kyprianidis, and J. P. Vigier, The anomalous photoelectric effect Quantum potential theory versus effective photon hypothesis, Phys. Lett. A 105A(12), 15-18 (1984). 

The origins of quantum theory blackbody radiation and the photoelectric effect... 

The Origins of Quantum Theory Blackbody Radiation and the Photoelectric Effect... 

Three discoveries mark the transition from classical to modem physics quantum theory, radioactivity, and relativity (Fig. 4.1). Quantum theory had its origin in the study of blackbody radiation and the photoelectric effect. 

An apparently quite separate (but in science no two phenomena are really ever unrelated) phenomenon that led to Eq. 4.3, which is to say to quantum theory, is the photoelectric effect the ejection of electrons from a metal surface exposed to light. 

Planck s explanation of the blackbody radiation curves (1900 [4]) and Einstein s explanation of the facts of the photoelectric effect (1905 [7]) indicated that the flow of energy in physical processes did not take place continuously, as had been believed, but rather jerkily, in discrete jumps, quantum by quantum. The contributions of Planck and Einstein were the signal developments marking the birth of quantum theory and the transition from classical to modem physics. 

Two papers by Albert Einstein ultimately led to acceptance of the idea of quantization of energy for radiation, and were central to the development of the quantum theory (ironically, in later years Einstein became the most implacable critic of this same theory). The first of these papers, in 1905, concerned the photoelectric effect. Light ejected electrons from a metallic surface if the light had a greater frequency than some threshold frequency v0 which depended on the particular metal. The kinetic energy K of the emitted electrons was proportional to the excess frequency, v — v0 (Figure 5.4). Only the number of emitted electrons, not the kinetic energy, increased as the intensity increased. 

Einstein s explanation of the photoelectric effect was not his only contribution to chemistry. His Ph.D. dissertation, submitted in 1905, was entitled A New Determination of Molecular Dimensions. His investigation of Brownian motion (the random movement of microscopic particles suspended in liquids or gases) was intended to establish the existence of atoms as being indispensable to an explanation of the molecular-kinetic theory of heat. And the concept of relativity has shed light on the motions of electrons in the core orbitals of heavy elements, see also Quantum Chemistry. 

The photoelectric effect was explained by Albert Einstein in 1905 using the principles of quantum physics developed by Max Planck. Einstein claimed that light was quantized— that is, it appeared in bundles of energy. While these bundles traveled in waves, certain reactions (like the photoelectric effect) revealed their particulate nature. This theory was further supported in 1923 by... 

In 1905, only five years after Planck presented his quantum theory, Albert Einstein used the theory to solve another mystery in physics, the photoelectric effect, a phenomenon in which electrons are ejected from the surface of certain metals exposed to light of at least a certain minimum frequency, called the threshold frequency (Fignre 7.5). The number of electrons ejected was proportional to the intensity (or brightness) of the light, but the energies of the ejected electrons were not. Below the threshold frequency no electrons were ejected no matter how intense the light. 

The photoelectric effect conld not be explained by the wave theory of light. Einstein, however, made an extraordinary assumption. He snggested that a beam of light is really a stream of particles. These particles of light are now called photons. Using Planck s quantum theory of radiation as a starting point, Einstein deduced that... 

Using quantum theory, Einstein solved another mystery of physics—the photoelectric effect. Einstein proposed that light can behave like a stream of particles (photons). 

The development of the quantum theory was at first slow. It was not until 1905 that Einstein2 suggested that the quantity of radiant energy hv was sent out in the process of emission of light not in all directions but instead unidirectionally, like a particle. The name light quantum or photon is applied to such a portion of radiant energy. Einstein also discussed the photoelectric effect, the fundamental processes of photochemistry, and the heat capacities of solid bodies in terms of the quantum theory. When light falls on a metal plate, electrons arc emitted from it. The maximum speed of these photoelectrons, however,... 

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