《大学物理西尔斯.ppt》由会员分享，可在线阅读，更多相关《大学物理西尔斯.ppt（21页珍藏版）》请在课桌文档上搜索。
1、Introduction：,1)the quantum theory In 1900，Plank put forward the concept of quantum,explaining the black-body radiation,which laid foundation to the quantum theory.In 1905，Einstein explained the photoelectric effect by the concept of photon,which led the the quantum theory to a new stage;In 19201926
2、，the discovery and analysis of Compton effect proved the theory of photon to be correct.The theoretical analysis coincided experiments perfectly.,28-3 Hydrogen Atomic line Spectra and energy levels,3)electron In 1897，J.J.Thomson discovered electron,leading people to the microworld.What,Quantum physi
3、cs,Newtonian mechanics for Microworld,With the development of spectroscopy people realized that spectra actually discover the interior structure of atoms.,2)Spectrum,atom,electron,Electron is negatively charged.Its mass is about one two-thousandth of that of Hydrogen atom.,electric neutrality,Q1：The
4、re must be something with positive charge in the atom.How does the mass of the atom distribute?,Q2：How does the charges of the atom distribute?,1)Atomic Spectra：,emission spectrum：the spectrum formed during the process of radiation of electromagnetic waves.,absorption spectrum：the spectrum formed du
5、ring the process of absorption of electromagnetic waves with certain wavelengths.,1.Atomic Spectra of Hydrogen,Experiments show that the emission spectrum is corresponding to absorption spectrum：Different atoms have different spectra which are the characteristic to identify the atoms.,Feature of the
6、 atom spectra:line spectra,Balmer series,Ha：656.210nmHb：486.074nmHg：434.010nmHd：410.120nm,We can get four lines within the visible light in an electric discharge tube.条,In 1885 the Swiss teacher Johann Balmer found formula that gives the wavelength of three lines,which are now called the Balmer seri
7、es.,Limit of wavelength of Balmer series,1890:,Rydberg constant,Atomic Spectra of Hydrogen,Lyman series:UV,Paschen series:visible light,Brackett series:near-infrared,Pfund series:,Similar regularity has been found in the spectra of atoms of other elements.,2.Rules of Atomic Spectra,unified formula,A
8、toms have line spectrum；There is some relationship between every line;The wave number of each line can be expressed by the difference of two spectral terms.,Experiments show that:,Ritz combination principle：,The wave number of any line spectrum can be expressed by the difference of two spectral term
9、s which comes from the many inherent spectral terms of the element.,(This was discovered by Ritz in 1908.),3.Energy levels:,1913,Bohr,The line spectrum of an element results from the emission of photons with specific energies from the atoms of the element.,during the emission of a photon,the interna
10、l energy of an atom changes by an amount equal to the energy of the photon.,Each atom must be able to exist only with certain specific values of internal energy-energy level.,1)Ground-state level:,Every atom has a lowest energy level that includes the minimum internal energy state that the atom can
11、have.,2)Excited level:,All higher levels are called excited level.,A photon corresponding to a particular Spectrum line is emitted when an atom makes a transition from a state in an excited level to a state in a lower excited level or the ground level.,3)Lifetime:,The average time spent in an excite
12、d level is called the lifetime of the level.,4)absorption spectrum:,In general,a photon emitted when an atom makes a transition from an excited level to a lower level can also be absorbed by a similar atom that is initially in a lower level.,玻尔（Niels henrik David Bohr，1885-1962）,丹麦理论物理学家，现代物理学的创始人之一
13、。在1913年发表了论原子结构与分子结构等三篇论文，提出了在卢瑟福原子有核模型基础上的关于原子稳定性和量子跃迁的三条假设，从而圆满地解释了氢原子的光谱规律。玻尔的成功，使量子理论取得重大发展，推动了量子物理的形成，具有划时代的意义。玻尔于1922年12月10日诺贝尔诞生100周年之际，在瑞典首都接受了当年的诺贝尔物理学奖金。1937年，他来中国作学术访问，表达了对中国人民的友好情谊。,The positive charges and the mass of the atom distribute uniformly in a sphere with the radius 10-10 m,and
14、 the electrons are immersed in the sphere.,1)Thomson model：raisins-cake model,1.Two important models for atoms:,28.4 the nuclear atom,1903:J.J.Thomson,It cannot explain why the positive and negtive charges do not neutralize;It cannot explain the presence of series of the hydrogen spectrum；It cannot
15、explain the large-angle scattering of-particles.,Limitation:,Scattering of-particle:,Most-particles are scattered through only a small angle when passing through the gold foil.A few-particles are scattered through an angle greaterthan 900，even nearly 1800.,The experiment of large-angle scattering of
16、-particles proved the Thomsons model incorrect.,2)the nuclear atom,Planet model of atom,The positive charges all concentrated in a small space-nucleus.It occupies only about 10-12 of the total volume of the atom or less.It contains more than 99%of the total mass of the atom.Electrons revolve around
17、the nucleus.,This mode can explain the large-angle scattering of-particles.,1911:Rutherford,According to classical physics,the electron with an acceleration should radiate electromagnetic waves.The frequency of the electromagnetic waves should equal the frequency of revolution.The energy of the elec
18、tron should decrease continuously and it should emit a continuous spectrum.Its orbit should become smaller and smaller and it should spiral rapidly into the nucleus.,2.Difficulty facing the nuclear model:,Collapse of atom,In fact,atoms are stationary.The line spectra of atom is regular.,卢瑟福（E.Rutherford，1871-1937）,英国物理学家，出生于新西兰。1859年成为卡文迪许实验室主任J.J.Thomson的研究生。1899年1月发现铀盐放射出射线和射线，并提出天然放射性的衰变理论和衰变定律。天然放射性的发现与电子和X射线的发现，是20世纪三项最伟大的发现。他于1908年获得诺贝尔化学奖。卢瑟福还判定粒子是带正电的氦原子核，他根据粒子散射实验提出原子的有核模型。卢瑟福被誉为原子物理之父，又是开创原子核物理学的奠基人。,
