UNIVERSITY PHYSICS II CHAPTER 26 An Aperitif of Modern physics 826. 1 Some important discoveries at the end of the 20th century I. The discovery of the electron Spot of Filament To vacuum pump Measure the charge to mass ratio of electron q 2 VE BL2
1 1. The discovery of the electron Measure the charge to mass ratio of electron §26.1 Some important discoveries at the end of the 20th century 2 2 2 B L yE m q =
8 26.1 Some important discoveries at the end of the 20th century JJ. Thomson(1856--1940) 826. 1 Some important discoveries at the end of the 20th century J J. Thomsons original tube
2 J. J. Thomson (1856--1940) §26.1 Some important discoveries at the end of the 20th century J. J. Thomson’s original tube §26.1 Some important discoveries at the end of the 20th century
8 26.1 Some important discoveries at the end of the 20th century a Measured the charge of the cathode rays; b Make a static electric deflection of the cathode rays c Measured the charge to mass ratio of the cathode rays d. prove the universal existence of the electron The charge to mass ratio of electron =17588×10C/kg TThe mass of electron m=9.11×10kg 826. 1 Some important discoveries at the end of the 20th century The charge of electron q=-e=-1.602×10-9C The charge of electron is quantized. The discovery of electron was the first clear evidence that the indivisible atoms of nature had structure
3 a. Measured the charge of the cathode rays; b. Make a static electric deflection of the cathode rays; c. Measured the charge to mass ratio of the cathode rays; d. Prove the universal existence of the electron. §26.1 Some important discoveries at the end of the 20th century The charge to mass ratio of electron 1.7588 10 C/kg 11 = × m q The mass of electron 9.11 10 kg −31 m = × The charge of electron 1.602 10 C −19 q = −e = − × The discovery of electron was the first clear evidence that the indivisible atoms of nature had structure. §26.1 Some important discoveries at the end of the 20th century The charge of electron is quantized
826. 1 Some important discoveries at the end of the 20th century 2. The discovery of X-rays Pyrex glass envelope Electron Tungsten target X 8 26.1 Some important discoveries at the end of the 20th century The characteristics of X-rays: a. It is generated whenever high-energy cathode rays strike solid naterials b. Matter is more or less transparent to X-rays X-ray photograph of a human
4 2. The discovery of X-rays §26.1 Some important discoveries at the end of the 20th century The characteristics of X-rays: a. It is generated whenever high-energy cathode rays strike solid materials. b. Matter is more or less transparent to X-rays. §26.1 Some important discoveries at the end of the 20th century
826. 1 Some important discoveries at the end of the 20th century c. Photographic film is affected by X-rays, so its use as a detector was assured from the beginning d. The rays is not deviated by electric and magnetic fields. and so are uncharged The applications of X-rays: The wave nature of X-rays makes them useful tools for the study of the structure of crystals and molecules, where the atoms and molecules acts as three-dimensional diffraction gratings 8 26.1 Some important discoveries at the end of the 20th century 屏 晶体 2
5 c. Photographic film is affected by X-rays, so its use as a detector was assured from the beginning. d. The rays is not deviated by electric and magnetic fields, and so are uncharged. The wave nature of X-rays makes them useful tools for the study of the structure of crystals and molecules, where the atoms and molecules acts as three-dimensional diffraction gratings. The applications of X-rays: §26.1 Some important discoveries at the end of the 20th century §26.1 Some important discoveries at the end of the 20th century