大学物理西尔斯.ppt

IntroductionIntroduction：1) the quantum theory1) the quantum theoryu In 1900In 1900，Plank put forward the concept of Plank put forward the concept of quantum , explaining the black-body radiation, quantum , explaining the black-body radiation, which laid foundation to the quantum theory. which laid foundation to the quantum theory.u In 1905In 1905，Einstein explained the photoelectricEinstein explained the photoelectric effect by the concept of photon, which led the effect by the concept of photon, which led the the quantum theory to a new stage;the quantum theory to a new stage;u In 19201926In 19201926，the discovery and analysis ofthe discovery and analysis of Compton effect proved the theory of Compton effect proved the theory of photon to photon to be correct. The theoretical analysis coincided be correct. The theoretical analysis coincided experiments perfectly. experiments perfectly. 28-3 Hydrogen Atomic line Spectra and energy levels3) electron3) electron In 1897 In 1897，J.J. Thomson discovered electron, J.J. Thomson discovered electron, leading people to the microworld leading people to the microworld. What. WhatQuantum physicsNewtonian mechanics for Microworldelectron With the development of spectroscopy With the development of spectroscopy people realized that spectra actually discover people realized that spectra actually discover the interior structure of atoms. the interior structure of atoms.2) SpectrumatomelectronElectron is negatively charged. Its mass is about one two-thousandth of that of Hydrogen atom.electric neutralityQ1：There 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 1) Atomic Spectra ：emission spectrumemission spectrum：the spectrum formed during the spectrum formed during the process of radiation of electromagnetic the process of radiation of electromagnetic waves. waves. absorption spectrum absorption spectrum： the spectrum formed the spectrum formed during the process of during the process of absorption of absorption of electromagnetic waves electromagnetic waves with certain wavelengths.with certain wavelengths.1. Atomic Spectra of HydrogenExperiments show thatExperiments show that the emission spectrum the emission spectrum is corresponding to absorption spectrumis corresponding to absorption spectrum： Different atoms have different spectra which Different atoms have different spectra which are the characteristic to identify the atoms.are the characteristic to identify the atoms.Feature of the atom spectra: line spectra Balmer seriesHHHHH ： 656.210nmH ： 486.074nmH ： 434.010nmH ： 410.120nmWe can get four lines We can get four lines within the visible light in within the visible light in an electric discharge an electric discharge tube.tube. 条条In 1885 the Swiss teacher Johann Balmer found In 1885 the Swiss teacher Johann Balmer found formula that gives the wavelength of three lines, formula that gives the wavelength of three lines, which are now called the Balmerwhich are now called the Balmer series. series., 5 , 4 , 3 2222 nnnB 364.6BnmLimit of wavelength of Balmer series,n 1890:3,4,5,n7141.097 373 10 mRBRydberg constant22111()2Rn Atomic Spectra of Hydrogen, 4 , 3 , 2)111(22nnR , 6 , 5 , 4)131(22nnR Lyman series:Lyman series: UVUVPaschenPaschen series: series: visible lightvisible light , 7 , 6 , 5)141(22nnR , 8 , 7 , 6)151(22nnR Brackett series :Brackett series :near-infraredPfundPfund series: series: Similar regularity has been found in the spectra Similar regularity has been found in the spectra of atoms of other elements.of atoms of other elements.2. Rules of Atomic Spectra2. Rules of Atomic Spectra 1,2,;12,fiffnnnn，22111,iffivRnnnnunified formulaunified formula Atoms have line spectrum Atoms have line spectrum； There is some relationship between every line;There is some relationship between every line; The wave number The wave number of each line can be of each line can be expressed by the difference of two spectral expressed by the difference of two spectral terms. terms.Experiments show that:Ritz combination principle：)()(ifnTnT2(),ffRT nn2( )iiRT nnThe wave number The wave number of any line spectrum can be of any line spectrum can be expressed by the difference of two spectral terms expressed by the difference of two spectral terms which comes from the many inherenwhich comes from the many inherent spectral t spectral terms of the element. terms of the element. (This was discovered by Ritz in 1908.)(This was discovered by Ritz in 1908.)3. Energy levels :3. Energy levels :1913, Bohr1913, Bohru The lineThe line spectrum of an element spectrum of an element results from results from the emission of the emission of photons with specific energies photons with specific energies from the atoms of the element. from the atoms of the element.u during the emission of a photon, the internalduring the emission of a photon, the internal energy of an atom changes by an amoun