Einstein-Planck quantum theory radiation

Solvay s desire to submit his work on the fundamental principles what he called gravito-materialitique to the attention of Europe s leading physicists prompted Nernst to envision an international conference on the current problems of kinetic theory of matter and the quantum theory of radiation. The idea struck an immediate responsive chord in Solvay s mind, and he charged Nernst to explore it further with Planck, Lorentz, Einstein, and the other prominent physicists. Nernst was quick to pursue the idea immediately on his return from Brussels to Berlin. 

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. 

Further work on similar types of cells has been carried out, in which not only is use made of the Nernst Theorem but likewise of the Einstein theory of atomic heat of solids (as modified by Nernst and Lmdemann) This will be taken up after we have discussed Planck s Quantum Theory of radiation and Einstein s application of it to the heat capacity of solids (Vol. Ill)... 

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... 

Planck s revolutionary idea about energy provided the basis for Einstein s explanation of the photoelectric effect in 1906 and for the Danish physicist Niels Bohr s atomic model of the hydrogen atom in 1913. Their success, in turn, lent support to Planck s theories, for which he received the Nobel Prize in physics in 1918. In the mid-1920s the combination of Planck s ideas about the particle-like nature of electromagnetic radiation and Erench physicist Louis de Broglie s hypothesis of the wavelike nature of electrons led to the formulation of quantum mechanics, which is still the accepted theory for the behavior of matter at atomic and subatomic levels. 

Another application of this idea occurs in a new derivation of Planck s radiation formula this is duo to Einstein, and has given effective support to the ideas of the quantum theory and in particular to Bohr s frequency condition. 

In order for a photochemical reaction to occur the radiation must be absorbed, and with the advent of the quantum theory it became possible to understand the relationship between the amount of radiation absorbed and the extent of the chemical change that occurs. It was first realized by A. Einstein (1879-1955) that electromagnetic radiation can be regarded as a beam of particles, which G. N. Lewis (1875-1940) later called photons each of these particles has an energy equal to /iv, where v is the frequency of the radiation and h is the Planck constant. In 1911 J. Stark (1874-1957) and independently in 1912 Einstein proposed that one photon of radiation is absorbed by one molecule. This relationship, usually referred to as Einstein s Law of Photochemical Equivalence, applies satisfactorily to electromagnetic radiation of ordinary intensities but fails for lasers of very high intensity. The lifetime of a moleeule that has absorbed a photon is usually less than about 10 sec, and with ordinary radiation it is unlikely for a molecule that has absorbed one photon to absorb another before it has become deactivated. In these circumstances there is therefore a one-to-one relationship between the number of photons absorbed and the number of excited molecules produced. Because of the high intensity of lasers, however, a molecule sometimes absorbs two or more photons, and one then speaks of multiphoton excitation. 

In 1905, Albert Einstein expanded on Planck s theory by introducing the radical idea that electromagnetic radiation has a dual wave-particle nature. Light exhibits many wavelike properties, but it can also be thought of as a stream of particles. Each particle carries a quantum of energy. 

The old quantum theory includes Planck s black-body radiation theory, Einstein s theory of the photoelectric effect, and Bohr s theory of the hydrogen atom. 

The old quantum theory consists of theories with arbitrary assumptions of quantization that were devised to explain phenomena that classical physics could not explain. The old quantum theory includes the black-body radiation theory of Planck, the photoelectric effect theory of Einstein, and the hydrogen atom theory of Bohr. 

In spite of this agreement between theory and experiment, not all physicists were willing to accept the quantum hypothesis. Indeed Planck himself believed initially that it applied only to the atomic oscillators in the cavity walls and not to the radiation inside the cavity. However, Einstein (1905) soon showed that the quantum theory could explain certain puzzling features of the photoelectric effect in a very simple way. 

In 1905, while an examiner at the Swiss Patent Office, Einstein in his spare time devised a theory to explain photoemission. His theory adopted Planck s quantum theory of a blackbody radiator and assumed that radiation itself was quantized. When a quantum of energy (hv) falls on a metal surface, its entire energy may be used to eject an electron from an atom. Because of the interaction of the ejected electron with surrounding atoms (their electronic distributions), a certain minimum energy is required for the electron to escape from the surface. The minimum energy to escape (< ) depends on the metal and is called the work function. The maximum kinetic energy of an emitted photoelectron is given by Einstein s equation... 

The early years of the twentieth century saw giant advances in man s understanding of nature which must be mentioned in any synopsis of the scientific history of this era. Thus, in 1901, M. Planck (NLP 1918 ) published his first paper on the black-body radiation law which ushered in the era of quantum mechanics. In 1905, A. Einstein (NLP 1918 ) published his Anna Mirabilis Papers on the photo effect, on Brownian motion, and on the theory of special relativity and the equivalence of matter and energy. 

The year 1913 marks a major climax in the history of science. The application of Planck s quantum hypothesis to blackbody radiation, and later by Einstein to the photoelectric effect, had met with disbelief and in some quarters even with scorn. Bohr s application to the theory of the hydrogen atom compelled belief and worked a revolution in thought. In the following ten years this new knowledge was quickly assimilated and applied with spectacular success to the interpretation of spectra and chemical periodicity. 

The photoelectron effect was first discovered by Henrich Hertz [11] in early 1887 in order to verify the implications of Maxwell s theory and relations. Hertz noticed a spark of light on metal contacts in electrical units when exposed to light. The dawn of a new era actually came in 1905. Albert Einstein brilliantly utilized Planck s new quantum energy concept to explain how low radiation intensity and high frequency can actually eject electrons from a metal piece. The converse failed to produce any electrons. Max Planck received the Nobel Prize on quantization of energy [12] in 1918 and Einstein received the Nobel Prize on photoelectric effect in 1921. The single relationship proposed so long ago by Einstein is still today the fundamental basis of photoelectron spectroscopy,... 

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