Quantum theory blackbody radiation

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

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

The Rayleigh-Jeans picture of the radiation field as an ensemble of different modes of vibration confined to an enclosure was applied to the blackbody problem in Chapter 1. The quantum theory of radiation develops this correspondence more explicitly, identifying each mode of the electromagnetic field with an abstract harmonic oscillator of frequency coa- The Hamiltonian for the entire radiation field can be written... 

Planck Max Carl Ernst Ludwig (1858-1947) Ger. phys., best know for Planck s constant representing quantum action, blackbody radiation, thermodynamics, physics before his quantum theory is often called classical... 

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. 

Max Planck, bom Kiel, Germany, 1858. Ph.D. Berlin 1879. Professor, Kiel, Berlin. Nobel Prize in physics for quantum theory of blackbody radiation 1918. Died Gottingen, 1947. 

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. 

When Planck used his equation to calculate the spectrum of blackbody radiation, he came up with a result that agreed perfectly with experimental results. More importantly, he had discovered quantum mechanics, because this simple equation forms the basis of quantum theory. When applied to the physics of blackbodies, it implies that energy is not continuous but comes in tiny, irreducible packets, or quanta (a word coined by Planck himself), that are directly proportional to the frequency of an oscillator. 

Max Planck in 1900 derived the correct form of the blackbody radiation law by introducing a bold postulate. He proposed that energies involved in absorption and emission of electromagnetic radiation did not belong to a continuum, as implied by Maxwell s theory, but were actually made up of discrete bundles—which he called quanta. Planck s idea is traditionally regarded as the birth of quantum theory. A quantum associated with radiation of frequency v has the energy... 

We have introduced you to the concepts and methods of quantum mechanics this branch of physics was developed to explain the behavior of matter on the nanometer length scale. The results of a number of key experiments demanded the creation of a new physical theory classical mechanics and electrodynamics failed completely to account for these new observations. The pivotal experiments and observations included the spectrum and temperature dependence of blackbody radiation, the very existence of stable atoms and their discrete line spectra, the... 

In 1900, Max Planck (1858-1947) discovered a formula (now often called the Planck radiation law) that modeled curves like those shown in Figure 24-21 nearly perfectly. He followed this discoveiy by developing a theory that made two bold assumptions regarding the oscillating atoms or molecules in blackbody radiators. He assumed (1) that these species could have only discrete energies and (2) that they could absorb or emit energy in discrete units, or quanta. These assumptions, which are implicit in Equation 24-3, laid the foundation for the development of quantum theory and eventually won him the Nobel Prize in Physics in 1918. 

More than a century has passed since Planck discovered that it is possible to explain properties of the blackbody radiation by introducing discrete packets of energy, which we now call photons. The idea of discrete or quantized nature of energy had deep consequences and resulted in development of quantum mechanics. The quantum theory of optical fields is called quantum optics. The construction of lasers in the 1960s gave impulse to rapid development of nonlinear optics with a broad variety of nonlinear optical phenomena that have been... 

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. 

Blackbody Radiation and the Quantum Theory of Energy The first of the puzzling observations involved the light given off by an object being heated. 

Plots of equation 9.23 are shown in Figure 9.15. Note that they are the same as the plots of blackbody radiation, but understand that Planck s equation predicts the intensity of blackbody radiation at all wavelengths and all temperatures. Thus, by predicting the intensities of blackbody radiation, Planck s quantum theory correctly models a phenomenon that classical science could not. 

Planck s quantum theory answered one of the great unknowns of earlier science, that of blackbody radiation. There were still several unanswered... 

Blackbody radiation is the term used to describe the dependence of the radiation energy emitted by an object on wavelength at a certain temperature. Planck proposed the quantum theory to account for the dependence. Shown in the figure is a plot of the radiation energy emitted by our sun versus wavelength. This curve is characteristic of objects at about 6000 K, which is the temperature at the surface of the sun. At a higher temperature, the curve has a similar shape but the maximum will shift to a shorter wavelength (a) What does this curve reveal about two... 

Maxwell s equations describe the propagation of electromagnetic radiation as waves within the framework of classical physics however, they do not describe emission phenomena. The search for the law that defines the energy distribution of radiation from a small hole in a large isothermal cavity gave rise to quantum theory. The function that describes the frequency distribution of blackbody radiation was the first result of that new theory (Planck, 1900,1901). 

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