大学物理Chap33amp;34-Quantum.ppt

Applications of the idea of electron’ wave-nature: (P774) The idea that electrons have wave properties led to the development of electron microscope (显微镜) by German physicist E. Ruska (1906-) in 1932, A scanning electron microscope has been further developed later, which produces images with 3D quality. which can produce images much greater magnification than a light microscope (resolution can reach 0.2nm). De Broglie got the Norbel Prize of physics of 1929. 33-5 The Hydrogen Atom The idea that matter is made up of atoms was accepted by most scientists by 1900. With the discovery of the electron in the 1890s, scientists began to think of the atom itself as having a structure and electrons as part of that structure. Early models of the atom (P775): J. J. Thomson, soon after his discovery of electrons in 1897, visualized a typical model of the atom in 1903 as a homogeneous sphere of positive charge inside of which there were tiny negative charged electrons. Thomson’s apparatus for measuring the ratio of mass to charge for the electron. Around 1911, E. Rutherford (1871—1937) and his colleagues performed experiments whose results contradicted Thomson’s model of the atom. α 粒子实验存在大角散射 The results based on the Rutherford’s “planetary” model is accord well with the one from scattering of ? particle. 1911年卢瑟福提出的原子的核模型 电子 原子核 Two main difficulties of “planetary” model: (2) It predicts that light of a continuous range of frequencies will be emitted, whereas experiment shows line spectra (原子光谱的谱线). (1) It predicts that atoms are unstable — electrons should quickly spiral into the nucleus —but we know that atoms in general are stable, since the matter around us is stable; Rutherford’s “planetary” model of the atom was a major step toward how we view the atom today. It wasn’t a complete model and showed some major problems, as we shall see. Atomic spectra— key to the structure of atom: Heated solids, liquids and dense gases emit light, due to oscillations of atom