Davisson-Germer

Louis de Broglie discussed the relations between energy, momentum, and wavelength for photons as well as for electrons and examined the results of the Davisson-Germer experiment on the diffraction of electrons by crystals, which were in perfect agreement with theory. 

FIGURE 4.21 Results of the Davisson-Germer experiment showing (a) the sin 9 dependence predicted by Bragg s law and (b) the dependence of the scattered intensity on the square root of the incident electron energy. 

Davisson/Germer electron diffraction by metal crystal... 

Rabi had fully confirmed the validity of the quantum (statistical) description (upon measurement) of matter (Davisson Germer, 1927 Thompson, 1928 Rupp, 1928 Rabi, 1936). 

Davisson/Germer Electron beam is diffracted by metal crystal. 

The observation from the Davisson-Germer experiment that electrons have wave properties led to the development of the electron microscope (Figure 12.11) An electron beam is passed through a series... 

A FIGURE 1.6 The Davisson-Germer electron difiCraction experiment. A beam of slow electrons has two possible paths between source and detector, via reflection off the first or second layer of atoms. The difference between the pathlengths is equal to roughly d cos 0 for the incident and for the reflected beams, or 2d cos0 overaU. 

At the time of Chadwick s discovery, the Davisson-Germer experiment was five years old, and the wavelike... 

De Broglie s insight and the Davisson-Germer experiment ultimately pointed out that matter has wave properties. For large pieces of matter, the wave properties can be ignored, but for small pieces of matter like electrons, they cannot be. Because classical mechanics did not consider matter as waves, it was inadequate to describe the behavior of matter. 

The Davisson-Germer experiment, which has since been repeated with other particles (including molecular hydrogen), shows clearly that particles have... 

Fii 9.6 In the Davisson-Germer experiment, a beam of electrons was directed on a single crystal of nickel, and the scattered electrons showed a variation in intensity with angle that corresponded to the pattern that would be expected if the electrons had a wave character and were diffracted by the layers of atoms in the solid. 

Look up the Davisson-Germer paper in Physical Review, vol. 30, p. 705, (1927) and look at the picture of the Ni crystal in their Figure 5. Then look up the word anneal in a dictionary and give your own brief description of what annealing metal means. 

The presentation by McMurry and Fay (2001) ignores the role played by the experiments conducted by Davisson, Germer, Thomson and Reid. On the other hand, the presentation by Umland and Bellama (1999) ignores the importance of Einstein s contribution which helped de Broglie to postulate wave-particle duality. This clearly shows that a historical reconstruction must emphasize at least the contributions of Einstein, de Broglie, Davisson and Germer. 

Criterion 3 Importance of Davisson-Germer Experiments and Their Struggle to Interpret Experimental Data. Of the 128 textbooks analyzed none described Satisfactorily (S) the difficulties involved in interpreting the Davisson-Germer experiments as evidence for the wave nature of the electron (see Table 2). Only one textbook came close to describing the unexpected diffraction patterns in the following terms and was classified as Mention (M) ... 

A sample of nickel [in Davisson-Germer experiments] was accidentally converted into crystalline form and, when subjected to the electron beam, produced totally unexpected diffraction patterns. .. similar to those observed in X-ray diffraction by crystals. .. Such behavior indicated that electrons, like electromagnetic radiation, possess wave characteristics (O Connor 1974, p. 50). 

Experiments are not only difficult to perform but also lead to alternative interpretations and consequently controversies (Criterion 3). Davisson-Germer had considerable difficulty in understanding their experimental data before it could be accepted as evidence for wave-particle duality. Even leading scientists (Planck, Bohr) were reluctant to accept the wave-particle duality as it conflicted with some of the predictions based on the previous dominant paradigm, namely the wave theory of light. 

Separately, the photoelectric effect and the Compton effect experiments unambiguously demonstrated that Ught photons behave like particles do. And around the same time the Davisson-Germer experiments showed how electrons exhibit wave properties. 

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